EX wife has moved new partner and kids in and my children are unhappy.

This is so sad and my heart is breaking for your poor kids. Your ex sounds like a selfish tw*t. I absolutely would seek to have full custody in this instance.

It’s a difficult one but I think the court would look favourably upon you if both your children were able to say they wanted to live with you. They wouldn’t split them up, not for discomfort.

You need to have a frank discussion with your ex. Maybe they could just spend more time at yours if that’s feasible?

No, I didn't say I knew for definite, but it was something I'd heard as a guideline. Blimey I'm getting taken the wrong way here but whatever, people are clearly enraged by this situation and I was offering support. However, I'm not on or agree with going on a war path like most of everyone else here, just suggesting finding out the things that would support the OP in getting this resolved without any further disruption.
I will look up the guidelines and educated myself if that makes you feel any better 😀

@ThatCalmCatyou think there are parents imprisoned for making their children share a room? That stipulation is for qualifying number of rooms for council housing.

Keep them both. Call a solicitor. Now. Seriously. Do not delay.

Your 7 year old is old enough that his feelings will be given a lot of consideration. And the 13 year old can definitely decide for herself.

My thoughts here are to try and resolve the situation without the kids losing contact with their mum.
There may be ways around it, without going in full force with a full custody order which will literally rip the kids lives in two and cause a rupture between the parents that will never heal.
Not everything is as black and white as that, is my point. OP has said no issues with mum until now, and given that he has had a partner for 2 plus years, I'd say perhaps 2/3 maybe more years have gone by with no prior issues.

I would speak to a solicitor specialising in family law. Things may have changed but when my parents had 50/50 custody I went from living with my Mum full time to my Dads full time as I wanted to live with him. My Mum didn’t contest the arrangement though, which is probably why it all went smoothly.
Your poor children, I can see why they are so upset .

This is the thing isn't it? Men move on really quickly with another woman and her kids, then expect everyone to be ok. SO.. yeah, hopefully @David850 is living on his own and can hae his kids with him?

Bloody hell. 11 months?!?!

id be going to court and keeping my daughter. If she sends her boyfriend call the police.

My 12 and 8 yo boys share a room by choice and this is totally normal.

there are enough issues for the OP without inventing cause for concern

What a load of tosh.

Where are her partner and his kids going to piss off to? There aren’t any other options but her children being forced to share their private space. She is a shit mother. She hasn’t even known this man a year. They are absolutely strangers and she’s risking her children’s emotional health, safety and comfort in their own homes just to have a boyfriend.

This is why my comment included concerns over his children’s safety. I’m very very worried for the 7ur old little boy sharing with a soon to be teen!

I think you need to go round to your ex's house with the kids, to have a discussion about everything and involve the children, if possible.

Clearly, your ex isn't considering the kids enough here, but to say she's a terrible mother for being in a relationship and wanting to live with her partner is a bit strong, though it is very soon if only 11 months into the relationship and her partner also has kids.

You need a way to resolve this, and it's all well and good everyone being on your side, but do you really need to encourage the kids not to stay with their mum?

I would take the tactic of keeping her on side and trying to support her in getting this ironed out.
In order to see Mum, even if they lived with you more than the current 50% , they will need to stay in her house. Surely not seeing her at all will be just as disruptive and upsetting.

They may be young still, especially your boy, but giving them a say and explaining the situation fairly and openly may make the world of a difference, rather than being told to just accept it when they had a different life before.

It's worth checking the law on children sharing rooms. Pretty sure that there is something about boys and girls not sharing over 12, but not sure about 2 the same sex.

Don't forget there are lots of large families that just have to get on with this.
For example, what if your partner went on to have more children with her new partner... and then the kids had to share with their half siblings? What would be the opinion then?

BTW, I am not like the mum, in my experience my children have had this happen with their dad and his new extended step family. My son, at 16 was expected to sleep on a sofa bed every time he stayed over, sharing a room with a child half his age. Needless to say when revising for his recent GCSEs, he stopped going as he never had any peace and could revise better here with me, his decision which I supported.

Bloody hell OP..... I am enraged for you. Truly appalling behaviour from your ex.

This is absolutely appalling. Far too soon to try and blend families. I’m disgusted. The idea that your ex would send her boyfriend (hardly a partner after 1 year!) round to collect your daughter is horrible. Without her mother there??

There is absolutely no way I would pack my daughter in a car with an unrelated man I didn’t personally know or trust. Especially not if she didn’t want to go. I’m not surprised your kids feel uncomfortable, the whole situation has been forced on them and it sounds like the boyfriends kids have quickly become priority.

In which case you can keep her at your house, I believe and there is nothing your ex can do.

What a selfish woman your ex is that is terrible for
your kids. I would not dream of doing this to my daughter. Horrid.

Feels quite inappropriate that your 7 year old is being asked to share with an 11 year old boy. If not already, then over the next few years this child is going to go through puberty and whatever that entails e.g. watching inappropriate material on his computer in their shared space. There's a reason why it's recommended that children over 10 have their own room.

I would say that whatever you can do to give your children a feeling of control at your house e.g. choosing something entirely on their own for their bedrooms at your house will be very helpful for them, given they are losing all sense of control in their mother's house.

How long has your ex been seeing this man? Have all the children not been introduced to each other over a long period before moving in?
@CarrotVan
I see OP has answered this and it was 11 months but even if they’d been introduced over a longer period of time it’s still not acceptable as the kids in this case are clearly unhappy with it .

I’d have hated it if my mum had moved some man with children in especially if I’d been forced to share my room with them, no matter how many years I’d known them for.

This is really unfair on the kids a court will always act in the childs best interests .
Your son and daughter are old enough to say where they want to stay and why.
Threatening you with her new partner that he will come and take the kids will be laughed at by a judge ...Apply for a order from the court in the meantime you are an equal in your children's lives you are important for there continued stability.
If they refuse to go back to mums it is a civil matter and the courts will want to know why.
Tell your kids they can stay with you you are not breaking any laws if they are unhappy it is in their best interests they stay with you for now x

Just chiming in to say I agree with everyone else, this is appalling and your ex is disgraceful as is her new partner - I bets his kids aren’t too happy either. I would let them stay at yours permanently if that’s what they want. I would encourage it as well.

If she takes it to court I think you’d win as you have space for them in your house and the older one especially will be considered competent to decide for herself and then they won’t want to split up the siblings.

I am not saying this is happening to your children or it will but as an fyi there can also be safeguarding concerns around these things.

I used to work for social services. I remember seeing an appalling case where all 3 siblings were sexually abused by their mums new partners children after they moved in.

Make it clear to your ex the reasons why the kids are not returning and consult a family lawyer if there’s any pushback.

That’s awful. Your children don’t have to return with your ex’s new partner. He has no PR and no relevance.
I think you need to get a formal court order as your ex clearly isn’t thinking if she thinks that this is appropriate. Does the ex’s partner have his kids 50/50 or full time?

You have no court agreement so if you can facilitate it then tell your ex the kids are staying with you all summer holidays. 50/50 does not have to be one day here, one day there, or one week here and one week there.

This is an awful thing to happen to your DC they must be feeling very upset and betrayed. It amazes me what people are allowed to do to their children that would seen as unacceptable if it happened to adults.
I would say don't rush into anything though, if you keep your daughter will your ex retaliate and stop you seeing your son? Has her behaviour changed since she has been with this Cuckoo of a man? Is there the possibility of her being controlled?
I think PP's have a good point about your DS not having as much agency as you DD in this situation. If you are stopped from seeing him and he is stuck in that household it will be horrible for him.
Any chance of family mediation or something similar with your ex and DC?

How awful this has happened to your children. To have their own mother and some man they really hardly know do this to them and their precious belongings. It's just literally trampling all over their feelings and their own private space.
Their mother has obviously not put her own children first, I wonder if it was the man's idea to move himself and his children into the house. Where did they all live before?
I find it really upsetting reading your OP, especially for your son is so young.
I hope you get legal advice, your daughter sounds like she can make up her own mind.
Their mother better watch out because the children won't forget this, having their safe space invaded. She might find in the future the children won't want anything to do with her, which will be her own fault.
Please protect them, also if the new man comes round and starts threatening, I'd be phoning the police.