To let my step daughter call me "mum" ?

Yes, he clearly hasn't processed his feelings properly. I guess there is 2 schools of thought at play here - one to tell him to belt up and get over it, and another to offer him somewhere safe he can start to process things. His mum's done her best in giving him 1:1 time, but I'd put money on him needing to verbalise his feelings without judgement, in order to process them and see he is being unreasonable. I can relate to this as my 17yr old DS also has spates of this type of behaviour. He too has not had the most stable upbringing with my split from his dad and a younger sibling to accept. Although we got back together again, and have done our best to minimise any impact (like OP has) it's clear he was affected. I can imagine my ds continuing this behaviour if it's not dealt with properly now.

I think you have misunderstood the unofficial MN rules Zone2. People are allowed to project and surmise and randomly assign characteristics if it results in a negative interpretation of him. But suggesting anything that might explain his off behaviour with a degree of empathy is “reaching.” 🙄

The 9yo and the 19yo both have needs. They both feel a gravitational emotional pull towards op
Both need sensitive approach,love and reassurance that’s what both are seeking
No one needs to be berated,called vile or told to get a grip

the young man is clearly processing unresolved issues of change, transition,attachment and perceives he is under threat. This is a wholly normal reaction that can be sensitively managed with him . He is experiencing human turmoil and conflicting emotions, he is signalling this loud and clear

I don’t think anyone isn’t feeling for the little girl.

But life isn’t a good guy/ bad guy Panto. They can both have needs and feelings that require balancing and working through. Just because you feel sorry for her, doesn’t need to mean he’s the bad guy through and through . Challenge yourself for fun and see if you can see any nuances or other pov.

Because children feel very threatened when their parents move on and have more children. I’m sorry that that can be inconvenient. You only need to read a few MN posts to witness the tensions that causes. Actually, even sibling rivalry within a family where children share the same biological parents is a completely natural drive. But it is more complicated when the other children are not from the same gene pool. That’s our animal brain. The way DS is reacting to the suggestion to allow the little SD to call his mum Mum suggests he has not yet processed some of this.

What consequence do you recommend op enacts? What’s a fitting consequence?
How will the consequence impact upon him and all the rest of the family?
How is the consequence arrived at, who determines what it is? What if he won’t or cannot abide by it?
is consequence time limited?
is consequence negotiable?

easy to rock up and demand consequences, less easy to deal with real life ramifications and impact

Hope I'm wrong, but it sounds to me like he is just naturally a controlling male type, that the battle of his stepsister calling OP "mum" is incidental, and what he is actually doing is honing his Controlling skills on OP. OP usually gives in to his demands but he is finding her more resistant to this one, and is determined to win. While he SEEMS to be lovely with his GF, - well, men like that usually do seem nice in public, don't they. Blowing hot and cold, also typical of controlling males. Again, really hope I'm wrong.

Blimey full character assassination.

And I'm not being petty here but plenty of teenage girls do that blowing hot and cold, tantruming thing too! It's because they're emotionally immature.

They need guidance, all of them.

I always told him that I wouldn't tolerate any bullying or mistreatment in our household.

Maybe he needs a consequence then. He's being unbelievably unkind to a nine year old girl whose biological mother has been off the scene. Who feels safe enough in your relationship to let you know she sees you as her mum.

What kind of adult sees that as a threat rather than a lovely thing?

I can't believe his is pleasant to her outside of this 'calling you mum' situation either, is he?

I imagine he is dismissive of her at best.

Imagine living in a home with someone who makes it obvious they don't like you. When you likely already have abandonment issues as a parent disappeared.

Poor little thing 😞

Childhood scars can take a long time to surface.

Why would he be scarred? By the sounds of it he had two loving parents, involved grandparents and relationships with other adults involved in his care.

The reaching on here is unbelievable.

So if no one knows don’t randomly assign unfavourable characteristics or guess his trajectory

But he just gets mad, and says " She is William's child , are you not happy with the 3 you have?.... I am going to start calling (Father's wife) mum then"

Tell him to crack on and go for it. All he would achieve would be looking like a complete eejit.

He sounds really unkind tbh. Poor little girl finally has someone she thinks of as her mum and instead of thinking how lovely that is, he's made it all about him and wants her to continue feeling left out and sad.

He's 19, not 9. Horrible.

Do you know this man? None of us can speak to his character. He may well use emotional blackmail as a tool for the rest of his life - or he might grow up and cut this nonsense out.

he might stop talking to his girlfriend every time she wants to have a night out with her friends - he might reserved the silent treatment for his mother.

no one knows

Yes you’re very wrong

Hope I'm wrong, but it sounds to me like he is just naturally a controlling male type, that the battle of his stepsister calling OP "mum" is incidental, and what he is actually doing is honing his Controlling skills on OP. OP usually gives in to his demands but he is finding her more resistant to this one, and is determined to win. While he SEEMS to be lovely with his GF, - well, men like that usually do seem nice in public, don't they. Blowing hot and cold, also typical of controlling males. Again, really hope I'm wrong.

You’ve done your very best by the sound of it OP, and your parents sound frankly amazing. But with all respect to that damage limitation, it was not a “normal” situation and he may be resenting that when he sees the younger ones with something more straightforward. - esp as his SS is now taking a step to round off the normality. He can do the maths as this poster points out. Childhood scars can take a long time to surface. Tbh you should be pleased it’s as early as it is really. He needs help processing and if you are finding him difficult to reach, perhaps some professional help.

Sounds like he feels his the interloper in the family now with the daughter calling you mum.

Before she was just the step child, and he split his time between two houses. They were on a more even standing in his eyes. But her mums dropped off the face of the planet and she now calls you mum. So now his the only person who’s different, his the one who doesn’t belong in the family. His feeling pushed out/othered by her changing role in the family.

Might not be rational but are we always even when we are 50/60 or 70. I doubt it.

Blended families are hard work and again as seen on other threads often at least one step/half feels like they don’t have a home they truly belong / are not the other in.

My mum died when I was 7. I'd have liked to call my stepmum "mum" but I never asked because I was very conscious that it would have peed off my real siblings and my step-siblings all who were older than me.

It was a real faff and I never quite knew how to talk about her to my steps. We all lived together on a permanent basis. There were no other parents in the mix.

I would not be tolerating a 19yo dictating to me. She wants to call you mum, you are comfortable with it so that's what should happen. A 19yo man wanting to single out a little girl? That is truly awful in my opinion and most folk I know of a similar age couldn't care less if a random stranger was to start calling their mum "mum" never mind a step sister who has been in their life for years. Sounds like power play, I would try getting on top of this behaviour

Piers? Is that you?

Let her call you Mum. Kids need a Mum. My Foster son calls me Mum. I've looked after him since he was 5. His biological Mum is dead not not stepping on any toes. It makes him happy and I think of him as another son anyway. Luckily by adult DC are very kind to him and include him in our family. I'd tell your son to stop being so mean and start being nice to the DC.

19 year old needs to grow up and get a grip frankly.

“What I dislike more and more about my son is that he is a bit hot and cold. If I don't do what he wants, he gives me the silent treatment. Then I feel guilty and always end up doing what he wants. So it's probably my fault for giving in every time.”

Hes learning to be very manipulative then- if he stone walls you/silent treatment he gets what he wants! (He‘ll do this to future partners too- very abusive!) Do not fall for it this time!! It’s often empty or short lived threats anyway if you stick to your guns & don’t give in. Also he needs to know that manipulation is wrong and not how you go about things!

This is a good suggestion, I would maybe add in something along the lines of "I do hear and realise you're finding this difficult to accept though, and it's clearly bringing up feelings for you, that I'm finding hard to understand. Maybe it's to do with how you're feeling about your place in the family and yours and my relationship? I can't stress how much I love you and that this will never change, but it might be an idea to chat all this over with a counsellor, if you feel so strongly that you have a problem with it? Lots of kids can grow up feeling pushed out when younger siblings come along, especially step siblings, so I get where these feelings might be coming from, but might be an idea to chat it over with someone who really understands all of this, what do you think? I love you and want nothing but happiness for you, so it's a concern you're feeling this way.

Okay, with your update, I agree this is the case for lovingly reinforcing a firm boundary. He needs to get over it. It does sound like he’s used to kicking up a fuss and getting his way and he needs to understand that’s not how life works, and sometimes we need to put other people’s feelings before our own.

Some kids think they are hard done by simply because they didn’t grow up in a typical two parent home with mum and dad, when it sounds like he had a perfectly stable and loving upbringing. If he goes out into the world thinking it owes him something, he’s going to get a shock, so think this is a good place to start being firm. Our wants do not trump the needs of others.

Ultimatum's and half threats aren’t going to work,Your speech is directive and doesn’t give him real options. Your big speech requires an immediate change. He’s not left with any manoeuvre or wriggle room . You’ve gone straight to dominant adult and forced him into truculent child Neither position is good for negotiations or a satisfactory outcome.

so what if he feels got at and cornered and says yes,he’ll go live at his dad
Does his dad want him to stay,has he been asked, or are you hoping this bluff works?

Ditch that speech. Make it all less convoluted, less ultimatum and be more calm and open

Try a calm and open approach. Things have been strained and we have both been feeling bad what can we do to make things better

Big you do this or that happens,they appeal to people and on,one as it looks overly simple and you think you’ll get the results you want. Chances are that he feels attacked, in his anxiety etc half hears and feels attacked. You do not unpick years of emotional anxiety and irrational fears by giving ultimatum. no matter how well intentioned the ultimatum is