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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Sisters 21st or partners 40th?

243 replies

EzWin2 · 05/06/2026 09:23

so my sister and DP have birthdays two days apart and both their 21st and 40th birthdays fall on the same weekend. I have been with DP for 11 years and we have children together. He made it clear he doesn’t want a party so I have decided to take him away to Italy just the two of us.
My sister is 21 on the same weekend and has arranged a party. She’s now really upset that I won’t be there and is not talking to me. I understand she’s upset but I have always made an effort to celebrate her past birthdays and took her to London for her 18th and spoiled her. She’s making me feel guilty and now I don’t know if I should re arrange the trip to Italy for the week after (DP won’t mind) or just stick to my original plans and hope she comes round eventually? I can then arrange something separate for just me and my sister to celebrate but right now she’s not talking to me.

OP posts:
ForeverPombear · 05/06/2026 11:54

Fast800goingforit · 05/06/2026 11:49

Probably because she'd already celebrated her 18th. Since when was celebrating an 18th and a 21st birthday a thing?

Surely by all the comments you can see by now that it's still a big thing for a lot of people so it can't be that much of a surprise that OP's sister sees it as a big birthday?

BoredZelda · 05/06/2026 11:54

SnappyQuoter · 05/06/2026 09:42

No, it isn’t. That’s just people copying American movies and trying to make 21st birthdays “a thing.” Most people roll their eyes because the big one here is 18.

Yes it is. 21st birthdays have been celebrated long before the falsehood of “Americanism” was a thing. It’s when you get “the key to the door”.

It is largely symbolic as the age of “adult” was moved from 21 to 18 in 1970, but it is still very much a thing.

@EzWin2I’m not sure why you would have booked knowing you have the two celebrations, particularly if your husband isn’t that bothered, so I can see why your sister might be annoyed. However, if you’ve put yourself in the position to have to choose, I guess you might prefer to choose your husband. Not the choice I would make, but my husband has always known if my sister need me, I choose her over him, mostly. The same way I understand he would choose his mum over me. We’d do it with each other’s blessing so wouldn’t have to ask.

stealthninjamum · 05/06/2026 11:55

JuneAlready · 05/06/2026 10:30

Why? It's his birthday too. Should his always be sidelined for her sister?

It’s not about always sidelining one family member for another, it’s about communicating. My brother has the same birthday as my ex mother in law. I’d always ask them if they have any plans before organising something. One year we went away for a significant birthday for one of them and I communicated that to the other and made different plans for their birthday.

Laurmolonlabe · 05/06/2026 11:57

It's unfortunate, but if you booked it before the party was arranged it's fair enough- life partner/father of your children trumps sister.
She's obviously quite an immature 21, she'll come around eventually.

Mapletree1985 · 05/06/2026 11:58

EzWin2 · 05/06/2026 09:23

so my sister and DP have birthdays two days apart and both their 21st and 40th birthdays fall on the same weekend. I have been with DP for 11 years and we have children together. He made it clear he doesn’t want a party so I have decided to take him away to Italy just the two of us.
My sister is 21 on the same weekend and has arranged a party. She’s now really upset that I won’t be there and is not talking to me. I understand she’s upset but I have always made an effort to celebrate her past birthdays and took her to London for her 18th and spoiled her. She’s making me feel guilty and now I don’t know if I should re arrange the trip to Italy for the week after (DP won’t mind) or just stick to my original plans and hope she comes round eventually? I can then arrange something separate for just me and my sister to celebrate but right now she’s not talking to me.

If the Italian holiday was booked and paid for before the big 21st was announced, there is nothing to be done, you are already committed.

ThreadGuardDog · 05/06/2026 12:05

MeetMeOnTheCorner · 05/06/2026 09:28

You didn’t need to go away and deliberately miss her party! That’s insensitive and why could you not do something on his birthday and go away the following weekend. That’s what mature people would do. I’m not surprised your sister is miffed. So you are being unreasonable.

Her sister is the one being unreasonable. It’s perfectly acceptable to want to do something special for your partners’ special birthday. Being miffed is one thing, but giving OP the silent treatment to get what she wants is manipulative and abusive. OP’s trip was booked before her sister announced her birthday plans, so it’s actually a fait accompli.

user1492757084 · 05/06/2026 12:06

I would surely have checked the dates were fine with 21 year old sister before booking Italy weekend.

Did you tell your sister about the holiday before booking?
Did you inform her so that she could have booked her party for a nearby weekend?

No question about it. For me, I would postpone the Italian weekend while I still can because 21st's are as special as a wedding almost in my family. And it wouldn't be a sacrifice.

HumbleStumble · 05/06/2026 12:10

Loulou4022 · 05/06/2026 09:29

Was the Italy weekend planned first? Your sister is being childish!
I get she’s upset that you won’t be there however not talking to you is quite frankly ridiculous and based on that alone I would be sticking to the Italy plans! Otherwise every time she doesn’t get her own way she’ll stop speaking so that people give in! Ludicrous!

Sounds like DP celebration been in the pipeline for about 40 yrs and DS for 21 or so.

Fast800goingforit · 05/06/2026 12:11

MyMilchick · 05/06/2026 11:51

Since always in my experience 💁

Huh?! They both celebrate coming of age. Why would you do both?

ThreadGuardDog · 05/06/2026 12:12

Lovethystupidneighbour · 05/06/2026 11:45

Over dramatising for no good reason

I agree to be honest. Often these threads are about men giving women the silent treatment and they are mostly told that it’s manipulative and abusive. Why is it any different when a woman does it. A poster upthread has advised OP to ‘grovel’ to her sister. Why ? Would any woman posting here grovel to a man subjecting them to the same treatment ?

MyMilchick · 05/06/2026 12:14

Fast800goingforit · 05/06/2026 12:11

Huh?! They both celebrate coming of age. Why would you do both?

Why do people celebrate 30ths or 40ths? Its'a silly question.......... they just do 💁

Skybluepinky · 05/06/2026 12:14

No idea why you booked a trip over a weekend when your sisters 21st is when it’s normal to have a 21st Birthday party.

WithLoveFromMyselfToYourself · 05/06/2026 12:17

She’s sound very immature for 20. Is she “challenging” when she doesn’t get her way?

Don’t capitulate, your mum is probably backing her because the consequences of your sister being pissed off are bad for her. Sadly it’s often the most unreasonable people who get pandered to because they make people miserable when they don’t get their way.

Mosaic80 · 05/06/2026 12:19

I think Yanbu - you should stick with the Italy plans. Apologise to your sister (sounds like you already have done this) and arrange a nice day out for the 2 of you to stretch her birthday out! It’s a 21st party, she will be socialising with her friends surely and won’t notice her big sister not being there too much.

Maybe you could treat her to something to prepare for the party like getting her nails or lashes done or whatever she likes to do.

your sister is being a bit unreasonable about this imo (maybe partly youth/immaturity). Fair enough to express disappointment but she ultimately has to accept your plans.

diddl · 05/06/2026 12:19

I wouldn't move plans for someone who stops talking to me rather than discussing possible changes.

Did she check before she arranged her party?

Fast800goingforit · 05/06/2026 12:23

ForeverPombear · 05/06/2026 11:54

Surely by all the comments you can see by now that it's still a big thing for a lot of people so it can't be that much of a surprise that OP's sister sees it as a big birthday?

My experience is difference. Surely you can see that? On the basis the sister has behaved like a complete arse I'd go to Italy. She'll get over it. And if she doesn't then she needs to get a grip.

DryTerryandJUNE · 05/06/2026 12:24

Are your children involved in any of the events? Would they enjoy the party?
Mine would probably just prefer Italy.
I wouldn't love spending an evening with a load of 20 year olds either.
I can't imagine a 21 year old being upset that an older relative was missing the party either.
But I appreciate that my family might be less into parties generally that your family 😄

FancyKeyboard · 05/06/2026 12:24

Literally no idea whatsoever what my brother did for his 21st. He certainly wasn't at mine. It all depends on the relationship. I would keep the trip.

FlynnD93 · 05/06/2026 12:24

EzWin2 · 05/06/2026 09:23

so my sister and DP have birthdays two days apart and both their 21st and 40th birthdays fall on the same weekend. I have been with DP for 11 years and we have children together. He made it clear he doesn’t want a party so I have decided to take him away to Italy just the two of us.
My sister is 21 on the same weekend and has arranged a party. She’s now really upset that I won’t be there and is not talking to me. I understand she’s upset but I have always made an effort to celebrate her past birthdays and took her to London for her 18th and spoiled her. She’s making me feel guilty and now I don’t know if I should re arrange the trip to Italy for the week after (DP won’t mind) or just stick to my original plans and hope she comes round eventually? I can then arrange something separate for just me and my sister to celebrate but right now she’s not talking to me.

You’ve known for 11yrs your hubby and sister have very close birthdays. You’ve also known his 40th and her 21st were big birthdays looming and were going to be the same weekend! You’ve also known booked a break away that he’s not bothered about but your sister is. I think YABU as you knew how old they both were and when their birthdays are so you could have attended her party and took hubby away the following week…IMO you’ve been thoughtless.

MikeRafone · 05/06/2026 12:25

Ellie1015 · 05/06/2026 09:40

I am in the UK and 21st definitely a big birthday. Must vary within UK too.

historically 21 was coming of age (become and adult)and the big birthday to celebrate - then the coming of age was lowered to 18 years old and so 18 became the big birthday.

Clearly the Ops sister wishes to celebrate twice, which is her prerogative - but other might only want to celebrate once

to say the change of coming of age happened in 1970 in England

AnotherBretonTop · 05/06/2026 12:25

Presumably you have not lived with your sister for years as you have children and have been together for 11 years. I would apologise for the oversight but stick with Italy.

I assume she would spend most of the party with her friends anyway.

horsesaanddogs · 05/06/2026 12:29

Don’t change the trip your sister is being precious

onetrickrockingpony · 05/06/2026 12:30

These responses are absolutely mad!!!!!!

When my friends and I all turned 21 we were at university. My Mum & Dad sent me flowers and a piece of jewellery. I saw them when I went back home for the Easter holidays. I think my sister probably sent me a card?

21st is not a big deal, it just sounds like a nice number. It used to be legally significant in the past and it continues to be in the US. But we are not in the past or the US.

Lovethystupidneighbour · 05/06/2026 12:30

ThreadGuardDog · 05/06/2026 12:12

I agree to be honest. Often these threads are about men giving women the silent treatment and they are mostly told that it’s manipulative and abusive. Why is it any different when a woman does it. A poster upthread has advised OP to ‘grovel’ to her sister. Why ? Would any woman posting here grovel to a man subjecting them to the same treatment ?

Because one action is different from a pattern of behaviour. Not everything is “abusive” and not everyone is a narcissist etc etc. Sometimes we can all just behave a bit shit. No need for the buzz words

MyMilchick · 05/06/2026 12:30

DryTerryandJUNE · 05/06/2026 12:24

Are your children involved in any of the events? Would they enjoy the party?
Mine would probably just prefer Italy.
I wouldn't love spending an evening with a load of 20 year olds either.
I can't imagine a 21 year old being upset that an older relative was missing the party either.
But I appreciate that my family might be less into parties generally that your family 😄

She says in the OP that the Italy trip is just the two of them

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