to feel like I’m picking between children over relationship with DH

Are you the poster currently unplanned pregnant for her new boyfriend who started off supportively and then became a massive red flag?

I’d be knocking the three nights where he comes to your house and you camp at your mum’s on the head straight away! Why on earth would he be in a rush to sort his own shit out when he’s playing you like a fiddle. Stop that.
Wrt your children, your DS has to learn to accept that relationships sometimes fail. It’s life. I’d be working on that to be fair.
Right now they’re in No-Man’s-Land. You need a complete split and help the children to move forward.

I remember your last thread and your ex was horrible to your DD. She was glad he moved out, and he is an ex for a reason.

Your DS will have to accept relationships fail.

You don’t let the children make the decision for you.

Generally speaking, once you’ve ripped off the sticking plaster and left, it’s better not to confuse them further by getting back together.

OP, you literally have a thread from full of perfectly good advice. It's really insulting to people trying to help you that you won't listen to it. That suggests to me what you want to do isn't what people are saying so you're reposting looking for different answers. You're not going to get any clarity if you keep filling up your head with lots of advice and not taking it onboard, just continually reposting. The longer you let this go on the more everyone involved is hurt, let that be your impetus to just make clean breaks with both men and heal your relationship with your son.

Don't let him stay at your house; it's not fair to you or your daughter. If he genuinely can't get his own place to live where he can have the children with him 50% of the time, can he maybe host them during part of the week at a family member's house - like his mum or dad or a sibling?

I'd be as confused as your daughter is about the difference between her dad and brother sharing lots of hobbies vs her dad's and brother's interests being the same thing. But either way, he's her dad. If he can't or won't parent her, don't force her to see him. But absolutely do make sure he pays the child support due.

Stop the stays in your home, that's ridiculous. He finds a place to live where DS can stay over and DD if she wants. If DS chooses to live with him then so be it.

I’m not surprised your DC are confused and upset. Your boundaries are not strong enough with the ex for the DC to understand theirs.

Put your own oxygen mask on first OP,
sort this out for you so you don’t have to keep accommodating your feckless ex in your space which is also upsetting your DD.

I’ve read your other thread OP and I can understand why you are so conflicted. But I think you need to stop trying to find the answer to it all right now. It sounds like you are understandably feeling emotional and highly anxious about the impact of things on everyone else. But there is no ultimate answer that will lead to happiness to all concerned. So stop trying to find it. I think you need to press pause on the new relationship. Maybe it will lead to something long term or maybe it won’t but this is not the time to be trying to work it all out. If he’s the man for you, he’ll wait. You need to be ok without a new relationship. And you need to focus on supporting your kids through the break up.
I think you should speak to a counsellor/therapist to try unpack things. The ex needs to stop coming over, it’s confusing for everyone. You all need space to digest things and find a way forward. No one is going to be fine with everything immediately. That’s impossible. It’s going to take time, lots of emotions and lots of conversation as you navigate this new path.

Stop going to your mothers.
Stop allowing him stay in your house making your daughter uncomfortable.
Tell your son he can move in with dad if he wants but he doesn't get to dictate your life.

This chaos continues because your son and husband have all the power.

Stop it.
Your poor daughter.

You need to be single and sort your head out.
The actual mess of what is truly going on will make you ill and then your children will really suffer.

Put your children first, this thread is just so not the complete picture.

To echo what everyone is saying, of course it still feels awfully entangled when you're sharing a home. You might not be staying at the same time, but it's clearly confusing the children.

Either he needs to find a suitable place, bring the children to a family members, or stick to day visits.

In your situation, I would:

• Put a stop to your exDH staying in your home (although that might mean selling if his share of marital money is also tied up in it). Give a him a fixed time frame to sort something out. After that he can take the kids out during the day/evening. Nesting works for some families (usually with a very clear but amicable break-up and young children), but it clearly isn’t working for your family and it’s just causing the kids to feel confused and unsettled.
• Have a kind but firm conversation with your son about the fact you and exDH won’t be getting back together, but that you still want to support him to have a good relationship with his dad.
• Don’t force DD to stay with her dad if she doesn’t want to (she’s likely to refuse to go once he has his own flat), but suggest to exDH that he does some things 1:1 with her to build their relationship.
• Possibly therapy if either/both children are still struggling to cope with the new situation (try to find someone who specializes in managing change/transitions for people with ASD, even if they’re online).
• DO NOT move anyone else in or make any other big life changes. This can wait until they’re much more settled or leave home. You can still have adult relationships when they’re spending time with their dad but introducing someone new now is going to massively exacerbate how unsettled and distressed they are feeling and will probably effect their relationship with you and your new partner long term.

Some families that split up, have this sort of arrangement, it’s called bird nesting isn’t it? DC stay put and parents split their time at the home

This.

Confusing, mixed messages.

You are making a drama out of this regardless of protestations.

New guy - stop seeing him, it isn't real or you wouldn't be mucking around like this.
ExH - be clear you are not getting back together. Explain why he needs a flat of his own and give him a 1 month timeline to sort it.
Kids - old enough to make their own decisions about where they want to be. Might be better for DD to have a day or evening out on her own with dad each week, and DS see him separately for now.

Before you split up how did DD cope with DH?

Your ex will not find his own place whilst he is squatting in yours

If you love your exH I would very slowly start a relationship again and if certain it would work out allow him to move back in. I would minimise the risk of splitting up again as much as possible.

You cant get back together to suit son and/or exh, there is no answer that will please everyone.

Son doesn't want any new partner. Daughter doesn't want exh back. Just live as you are just now and any relationship should be very slow and not involve the children for a long time.

She’s had multiple threads about it like she mentioned in her OP, the most recent one is still going where she talked about her new partner, that’s why several of us no about it.

He shouldn’t be coming back to your place to facilitate a relationship with his kids. He needs to find a suitable place to live to create his own relationship without YOU facilitating a relationship with them. Let’s be really honest, would he have a real relationship with DD if you didn’t facilitate it?

This.

He absolutely cannot be staying at your house. It’s giving your dc no chance to actually get used to the new status quo.

I don't recall op mentioning that she has a new partner just that her son has said he will never accept one should the situation arise.

Pick you OP.

Either way this situation is not a feasible long term solution and your effectively being driven from your own home to placate one of your children. Your DS whilst I truly feel for him is being given false hope whilst this arrangement exists.

It’s only been a year, your kids are still adjusting to a new normal which still isn’t settled because their dad is staying over and doesn’t have space for them. You need to sort out the longer term contact arrangements and give them time to settle.

Your son is under no obligation to accept a new person in your life, a year after separation is far too soon to be thinking about introducing a new partner to your kids anyway. Your sons feelings may change if he sees his dad settled somewhere new, but if not he’s entitled to not want another adult male in his life or his home.