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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

To believe sis(12) over SD(11)?

335 replies

Bestofgoodluck · 13/02/2025 19:08

SD is 11, have been with her dad for 5 years, mum is not involved. DP has to go away often for work and I work from home so look after SD while he’s away. This is mostly been fine, she has the option of staying with grandparents but chooses to stay with me.

I also have a 12 year old sister, our mum has quite a few problems and as I am older, she has stayed with me on and off since she was a baby.

They are completely different but have settled into a friendly but probably not friends relationship and there has never any major problems between them. I have been looking after both a them for about a week. They go to different schools and do different activities so don’t see each other that much but when we’ve been together everything has been fine and they both have seemed happy.

Sister went back to our mums today and SD came to me in tears and showed me some extremely nasty and embarrassing messages sent from my sister to her last night, I comforted her and said I would talk to my sister, she cried for me not to and said just not to make her see her anymore.
Sister said she had no idea what I was talking about and that there were no messages on her phone, was asking what they said and why she would do that, I’m 99% sure I believe her. I was already thinking the wording and content of the messages didn’t seem like things my sister would say and more likely that SD sent them to her self.

I feel completely torn between the two of them and can’t see how I can sort this between them or know who is telling the truth.

AIBU to choose my sister over my stepdaughter? And to say SD has to go to her grandparents if DP is away and my sister wants to stay with me?

OP posts:
Endofyear · 13/02/2025 19:37

I would get them both together in a room and look them in the eye and tell them this needs sorting out. I think you'll be able to tell who's lying. If you can't prove it either way, you can't just decide that your SD is lying. I wouldn't be sending her to her grandparents but I would be taking both phones at bedtime and keeping them with me so there can be no repeat behaviour.

Madamecholetsbonnet · 13/02/2025 19:37

Sorry, cross post. Ok, it does sound like DSD wrote them then.

Her dad needs to have a serious chat with her.

Sassybooklover · 13/02/2025 19:44

You have to treat both girls the same. If they were your daughter's would you automatically believe one over the other? I would sit them both down and have a conversation, and make it very plain that you will not tolerate nasty behaviour or lying. If neither owns up, then you take their phones away, and tell them that until someone tells you the truth, then you will be keeping both phones. Phones going forward are kept downstairs or on your bedroom at night.

ForeverPombear · 13/02/2025 19:44

I still don't think it sounds like DSD definitely did write them.

I think you don't believe either of them, have a chat with both of them and remove phones when they are both there and don't give them back until the morning. One of them is lying and you have no idea which, you may think you know but you don't and you could ruin a relationship with one of them.

Fingerscrossed22 · 13/02/2025 19:44

As PP said, in your situ I would be confiscating both phones until one of them told the truth and I wouldnt let them stay over at the same time again either

ItGhoul · 13/02/2025 19:46

Bestofgoodluck · 13/02/2025 19:35

To be honest it’s seems a strange thing for both of them to do to but as preteen girls they both have some form for lying and doing strange things. I’m not saying that’s I don’t think my sister could be mean, I just don’t think she would do it this way.
The content of the messages seemed to be things SD was upset and embarrassed about and not necessarily thing Sis would even care about.

I think your SD is at a tricky age, is probably very insecure, doesn't have a mum and probably feels like she might get pushed out by your sister, who she sees as a rival for your affections and something that disrupts what to her is the only family unit she's got. She doesn't have any mother figure in her life except you and she's terrified that she'll be replaced.

If she has lied then obviously that's not good behaviour, and clearly her fears aren't rational, but equally she's only an 11-year-old kid and I think it's pretty easy to see where all this might have come from.

I absolutely do not think you should send her off to her grandparents. She's already been rejected by her biological mum. I don't think you have to choose between your SD and your sister.

DillyDallyingAllDay · 13/02/2025 19:47

Haven't read all the replies and this is probably considered bad parenting- but surely what D is trying to achieve is either a) that your sister doesn't come stay with you when she's around or b) she doesn't want to see your sister at all
SD is adamant that you dont speak to sis so you could easily nip the whole situation. In the bud bu telling SD that your sister will still be coming to stay with you and you wouldn't mind if she stayed with her grandparents when your sister is around.
Would avoid you dealing with anything or taking sides though. Although SDs reaction might reveal more.

london111 · 13/02/2025 19:49

i know this isn’t your question but I am shocked that neither of them have passwords on their phone. That is basic security 101. It opens them up to all sorts of risks. You/the parents can know their passwords but they should have them. And this problem would not have occurred if they had passwords.

Ger1atricMillennial · 13/02/2025 19:50

Firstly good for you to step into parent the girls when their parents aren't around.

Agree with others this is parenting. You don't need to pick sides but establish and reinforce boundaries. It will become clear which one is breaking the rules.

Make it clear that these messages are disgusting and noone is to ever send anything like that again to anyone. Explain that you know someone is lying (look them in the face when you say this) but you can't tell which one of them it is. Then say something like "You are allowed phones because I permit it, but if this behaviour happens again then the house rule will be that phones are given up at bed time/ or only used in the common areas".

EndlessTreadmill · 13/02/2025 19:52

JLou08 · 13/02/2025 19:25

You don't need to choose anyone. If you had 2 children of your own and this happened you wouldn't be sending any of them off to grandparents. Your SD has shown you evidence so I would question why you are so inclined to believe your sister. Language used around adults as teens is different to the language used with other teens so I wouldn't see that as evidence she is lying.

This. Don't banish anyone. Treat them both as if they were your own kids, which in some ways they are. You need to get to the bottom of it, one of them is lying, but equally, you love them both and want to sort it out, as you all enjoy the setup and you don't want it to change.
I wonder if jealousy might be at stake here, from one of the - are they vying for your affection? Is one of them thinking that you prefer or show favoritism to the other? Could be SD feeling insecure, and being jealous of your perceived preference for your own sister (evidenced by the fact SD is the one you would immediately banish).

Wonderi · 13/02/2025 19:52

I would find it hard to believe that SD crept out in the middle of the night I text herself off of sisters phone and then deleted the evidence.

It is much more likely that sister texted SD and then deleted them herself (or will do).

PumpkinSpicedLatte · 13/02/2025 19:53

@Dramatic this is true actually you have a good point. I suppose pre teens don’t think this rationally. Back in my day it was reversed charges and knock-a-door 🤣🤷🏼‍♀️

Doggymummar · 13/02/2025 19:54

Bestofgoodluck · 13/02/2025 19:27

Sorry if I didn’t make it clear.
They are text messages from my sisters number, shown to me on my SD’s phone.
Both girls were staying here last night, I was believing that SD had sent them to her self from my sisters phone while she was asleep.

Highly unlikely, why would she do that?

Original poster
Bestofgoodluck · 13/02/2025 19:55

Sd is generally much more sensitive, she has been hysterical since and would not easily accept my sister being back in the house at the moment.

I only really see my sister when she stays here and don’t visit our mum often. She is pretty unbothered, just I didn’t send anything, why would I? If she didn’t send them then she doesn’t know the whole content of the messages but they were very nasty and If I properly accuse her and she didn’t do anything then she is also going to be very upset and I can’t actually make her come here, which would mean she is left home alone.

OP posts:
Ddakji · 13/02/2025 19:56

Agree to adding passwords (that you know) to the phones, and I would add that phones are brought downstairs (not left in the landing where they are easily accessible) overnight.

Comedycook · 13/02/2025 19:56

I don't think you should frame it as picking one over the other. Sit them both down calmly and say that you need to know the truth. Tell them that you won't get angry if they're both honest and then sort out whatever it is that causing one of them to act out

Dramatic · 13/02/2025 19:57

Bestofgoodluck · 13/02/2025 19:55

Sd is generally much more sensitive, she has been hysterical since and would not easily accept my sister being back in the house at the moment.

I only really see my sister when she stays here and don’t visit our mum often. She is pretty unbothered, just I didn’t send anything, why would I? If she didn’t send them then she doesn’t know the whole content of the messages but they were very nasty and If I properly accuse her and she didn’t do anything then she is also going to be very upset and I can’t actually make her come here, which would mean she is left home alone.

Had SD not been on her phone the whole day until your sister went home?

xRobin · 13/02/2025 20:02

ItGhoul · 13/02/2025 19:46

I think your SD is at a tricky age, is probably very insecure, doesn't have a mum and probably feels like she might get pushed out by your sister, who she sees as a rival for your affections and something that disrupts what to her is the only family unit she's got. She doesn't have any mother figure in her life except you and she's terrified that she'll be replaced.

If she has lied then obviously that's not good behaviour, and clearly her fears aren't rational, but equally she's only an 11-year-old kid and I think it's pretty easy to see where all this might have come from.

I absolutely do not think you should send her off to her grandparents. She's already been rejected by her biological mum. I don't think you have to choose between your SD and your sister.

Show quote history

This!
The worst thing OP could do would be to ship her off.
Maybe the lie needs to be outed by whomever told it and some bonding and security needs to be put in place.
It sounds like both girls have been somewhat shipped off to OP’s house for various reasons.

UndermyShoeJoe · 13/02/2025 20:05

If SD is lying she clearly has big issues with your sister. Which need resolving regardless.

If Sister is lying you’re asking sd to have someone bullying her in her home.

tricky.

Animatic · 13/02/2025 20:05

I wouldn't even try doing cross-questioning and looking in the eyes. I would seat them down and tell that this is not to be repeated, and phones will not go to bedrooms at night.

Theunamedcat · 13/02/2025 20:06

The phones need to be in a lock box overnight

My sons phone opens with his fingerprint I can unlock it with a code though so the only person it stops is his brother

It does sound like jealous behaviour fron SD is quite likely though

DivergentDilema · 13/02/2025 20:10

You do seem to be taking one side more than the other with very little concrete reason as to why.

But regardless of who did it, all behaviour is communication. I'm not saying that there shouldn't be consequences, but this hasn't come from a place of security and happiness. There's a bigger issue here that needs to be explored and dealt with compassionately.

Tiswa · 13/02/2025 20:11

You have a problem to sort out regardless of who sent them

first of this is your SD home you cannot ship her off to her grandparents

second not getting that and the impact your sister has coming to visit on her in her house may well be part of the problem

the thing is your SD should be the priority it is her who is the child not the sibling. Talk to her and work out what it is that is bothering her - because it is clear something is regardless of who sent the messages

beencaughttrollin · 13/02/2025 20:13

First, are you absolutely sure that the messages you reviewed on your SD's phone came from your sister's phone (or from one of her accounts - it's hard to talk about this clearly without knowing what type of messages they were)? There's no possibility that it could be a spoofed address, or an account set up to show your sister's name as a display but not actually from her phone/account? Is it possible they could have been sent by a third party - let's say, maybe, a friend of one of the girls who's irrationally jealous of the relationship? Or someone in your family trying to manipulate the situation?

If you're sure none of that is possible and one of the two girls sent the messages, I still would not take sides, at least not yet. DS has said she doesn't want to see your sister - OK, she doesn't need to right now as sis is home. But eventually sis will be back, so I would help your SD prepare for that. If she genuinely chooses to go to her GP's to avoid your sis, that's one thing - but why on earth would you say she HAS to go to the GPs?

NC10125 · 13/02/2025 20:18

If you have a strong feeling that SD is at fault, but she is also the child who is upset, then I personally would stop investigating now. If you pick one child out as lying (even if you are 100% sure) without proof it is going to make the situation worse.

I'd spend some one-to-one time with each of the girls reinforcing how much you love them; have some chats with both of them about self esteem; and about internet safety. And then do a piece of reconciliation work with both of them focused on something like women support each other rather than specifically about this. I'd also make it very clear to both girls that nothing either of them ever does would stop them both being welcome in the house.

In response to the messages themselves I'd make a big fuss about stopping it ever happening again. I'd change the evening rule so that phones are plugged in downstairs and I'd put some sort of parental controls onto both phones (if you can) so that you can see what is sent. Plus an opening code on both phones which you know but that the other child doesn't.

Next time your sister comes to stay I'd also invite someone over to change up the dynamics a bit so that there is a bit of a buffer.