To let my step daughter call me "mum" ?

He might. Or whatever is triggering this admittedly immature behaviour might deepen. It isn’t babying people to want to help them process things that have been difficult. As a society we tend to be very blasé about the impact on children of blended families.

I think it's fantastic she wants to call you mum and you are happy with this- bottom line is you are in fact a mum to her. Not blood related but that's it.

She's at an age where she can make up her own mind and it'll probably give her a sense of belonging even more so.

My first reaction to your ADULT ds was, he needs to grow up.
Caring me says write him a letter/ text reminding him he is loved, your eldest ds so always has a special place in your heart etc and while you don't want him to move out, you will always love him etc.

If you don't make your own choice your adult son will do more than this to control you.

I don’t doubt it. Kids are annoying though and tend to see the negative. My kid told me tonight I’m grumpy because I refuse them ice cream too much - I literally gave them ice cream at 10am this morning to be the cool mum!

I just mean clearly you’re a loving person (as your relationship with SD shows) and you WANT a great relationship with your son, so sometimes when you want to wring their neck, you just have to take a step back and accept they need you to say sorry and that you love them rather than tell them they’re wrong for feeling that way.

And if you tell him to bugger off and that he’s being petulant, and then he sees she starts calling you mum, he’s just going to feel that he was right in his feelings and feel justified in having felt jealous.

sorry you’re stuck between a rock and a hard place. Hope it works out really well for you all :)

Maybe he needs some time to think about it and articulate how he's feeling there. The OP is not doing anything wrong in this situation though

Op all you can do is keep on reassuring him that your love for him is unlimited and in no diminished by the presence of any of the girls. Her calling you the name of the role you've carried out since she was 2 chambers nothing for you two and everything for her. Is he wrong listen, perhaps write it down.

How's your relationship with his Dad? Would he have a word with him?

You're being ridiculous. I have a nearly 18 yo so not dissimilar in age with all that disruption plus some other situations on top of that to make life even more difficult for him. I can't even see how you have taken that I have zero compassion from my posts.

Not giving in to a 19 yos demands doesn't mean I would lack compassion, it just means I have higher expectations of a 19 yo adult than you do. Why are your expectations of a 19 yo man so low.

He's behaving like a brat. She's 9 it's only natural she would want to call you mum when her own mother isn't around.

That poor child has been abandoned by her own mother and obviously appreciates all you do for her. For the love of God do not pick another name or stop her calling you mum. She doesn't deserve another rejection.

Your son is 19 and an adult. He does not get to throw toddler temper tantrums like that.

Put your foot down hard. Maybe offer to attend family counselling so.you can all.unpick his jealousy. But ultimately the only person who has the right to prevent this is her father. If he is happy with it then let it happen.

For all the ways that matter to that little girl.you arr her mum.

I guarantee when she is sick you nurse her, when she is sad you hug her and cheer her up. You do school stuff. Put plasters on, hold her when she is scared. Cheer her successes.

Good on you @Lospecesenelrio you sound so lovely!!!

Good luck as I fear his behaviour will get worse. But stand your ground. You will always be his mum but he needs you far less than that poor little girl does.

Yes but it hasn’t resolved anything. I don’t envy her task, but it hasn’t resolved the situation. There something deep-seated in his resistance that needs addressing.

I think it's lovely that she calls you Mum, you obviously have given her a very stable and loving home. Your son needs to grow up emotionally wise, he should be proud of you for making a happy home. He'll mature one day hopefully and realise what a twat he's been lol.

This made me so emotional reading .
What a beautiful compliment she wants to call you mum.
Seeing the twins call you mum she must have desperately wanted to also call you mum. At her age I imagine it took alot of courage to do it . I’m absolutely delighted she has you in her life . I’m a step mum and it isn’t an easy role but so rewarding. Absolutely amazing you are stepping up and showing the love. Your son is 19. This little lady is 9. She needs you. Your son will come around .

Did it ever occur to you that there might be a reason for that?!

Yup

In this instance her need for a mother outranks his feeling of upset (by some margin)

I mean ultimately this ^ is the case.

However I can’t help but think back to the recent thread about the feelings of the first child(ren) when their parent remarries and has more children. And suddenly they aren’t the priority any more (or they don’t feel like they are, anyway) and they feel like they dont really belong anywhere.

I wonder if this is at play here.

The OP has tried talking to him, it's not like she has ignored him.

I would stand up to your son. He is 19 years old!! He is supposed to act more like an adult and not a child! Geez. I would have a serious word with him. I am shocked he would deny his stepsister the chance at having a mother daughter relationship with you. Sounds like he is jealous...but he is not a child and should not act like he is 10.

Exactly my feelings. He is being immature but I think it’s driven by very real emotions. They need sorting before you say ( to his mind) : “oh too bad about your feelings on the matter, I’m going to mother SD as my own whether you like it or not.” She’s clearly happy and secure at the moment, you’ve got her on an even keel, OP, ( well done) and it’s DS who is needing helping through his emotions. Ultimately if you just ignore that, his insecurity is kind of justified: you are prioritising her needs at her needs at the expense of his.

Is his issue with the fact that she calls you Mum, the fact that she wants you to adopt her, or both?

I see a lot of recent graduates - men and women in their very early twenties. I have been shocked over recent years at how their emotional development is delayed. They are less resilient, more entitled. Often outraged at having their work corrected or critiqued. It has gotten a lot worse in the last five years or so.

I have had two (yes two) mothers contact me about their adult sons. One to check I would meet him at reception on his first day😂.

I think we need to stop babying these young adults. This thread has really highlighted that for me. A 19 year old should have the emotional intelligence to understand this situation and the ability to work though his emotions in a calmer way. He needs to
understand his reaction isn’t either compassionate or age appropriate. He needs to learn that he is not the centre of this family - he is an important, equal member but he cannot dictate every relationship.

OP he obviously feels on the outside of the newer family unit. There have been so many threads on MN explaining how insecure/difficult it can be to be the child from a first relationship that ends, who then has to try and fit into 2 new families when their parents meet new people/have new children when they will never fully belong to either. Your twins, you and DH are a complete unit, and until now DS and DSD have been partly "outside that" by having other parents elsewhere. By you becoming her "Mum" he will be the last one that doesn't fully fit in. I'm not excusing his reaction but 19 is very young and this is clearly difficult for him. Your DSD sounds lovely and deserves to have a mum (which is essentially what you are already in all but name) but I think you need to handle this carefully with your DS so it doesn't damage your relationship with him. I was the oldest/only child from a previous relationship and my DM took on a large new step family and took on the role of mum including a name similar to "mummy". I never resented them, & I'm glad they've got her, but it wasn't handled well and really damaged my trust in my DM and my self esteem.

Given that the actual mother has gone from her life and you are fulfilling the role perfectly, I think it's lovely that she wants to call you mum.

If your son was a young boy I can understand he may feel a bit off about it but he's an adult and should understand that the little girl only wants to fit in with everyone else.

He hasn't even gone about it maturely, he's been nasty and manipulative and made threats and even more dreadful has blamed the girl who is only a 9 year old child.

He needs a reality check that he is acting very badly and it won't be tolerated.

Well I think it’s lovely she sees you as mum.

blood doesn’t always stand for much.

I agree with what @Devonshiregal said and it can be quite common for people to get a bit “stuck” at an age where something tricky happens they don’t or can’t resolve. So the son may be kind of stuck age 11/12 when this little girl came into his mums life and his life- and he was “too old” to show the jealousy or upset he actually felt at that time.. and instead it has kind of sat stagnant for these years but is coming out now… a bit like when we grown adults regress to whiny brats when our adult siblings annoy us the same way they did when we were 7/9 years old and we get all whiny and childish, regardless of our age. Or often people play out unresolved mum/dad issues with their partners in marriage arguments - sulking, crying etc… childish behaviours that are a throwback to our unresolved shit from childhood.
@Lospecesenelrio please don’t vilify your son, but take time to really listen to him, reassure him that he is your one and only son and you love him dearly, and he is the one who MADE you a Mum, but that you’re a good mum and one who knows this little girl needs you to be her mum also… and that love shared doesn’t lessen- it grows.

But she is mothering him. His problem is he wants to exclude a child ten years his junior from using the word Mum.

My comparison (evidently not put clearly enough 😄) was about his behaviour being unacceptable, and that it would be seen as such if anyone else complained about it. He'd be seen as an adult, not a child needing to be catered to - especially when it means putting a vulnerable little girl on the outer.

It's lovely that sd wants to call you mum. You are obviously doing a great job with her, and she is lucky to have you as a role model in her life. Your 19 year old needs to grow up.