DP’s son moving in

Exactly my thinking: the son is treating his mum like his servant and is being messy. Before he moves in, tell him he'll be moving out if there's any sign of house pig behaviour.

Yes - you need to be very sure that his dad will be equally holding him to civilised living in the house and not expecting you to do it, or expecting you to put up with it to keep the peace. First step - talk to your DH about what happens about setting and maintaining expectations.

It sounds like you may both have been assuming that you and your partner would primarily live alone, with short stays from your respective children. The difference seems to be that your partner made assumptions that the home would be open for longer term arrangements for the children and you weren’t. If this wasn’t discussed at all, you have both been making assumptions. As previous posts show, some posters would also assume that all parents would open their doors to their young adult whilst others wouldn’t.

I don’t think it’s unreasonable for your partner to want to house his child. It is also not unreasonable for you to decide this set up isn’t what you thought how things would be, and pull out of the purchase.

I think you need to separate the issue about communication, which is easier to fix, from issues arising from your living arrangements not being what works well for you.

YANBU OP, I would be very uncomfortable with this. Like you say not so much his son moving in but the complete lack of discussion about it. Also what would be concerning me is he's moving out from his mums because she moans at him a lot, so basically he's looking for a doss house where he's not expected to have to do anything. Also bit strange this has come all of a sudden when you and partner are buying a nice new house. He's 19 and working surely if he doesn't want to live with his mum any more he could be looking for a flat or something to rent

WHY is his mum moaning at him? If there is a perfectly good reason his own, loving mother isn't happy with him, it doesn't bode well for him living with you.

I would tell DP that you're pausing the exchange until you've resolved the issue of his son to your mutual satisfaction.

That's nice, I'm glad I know that you think it's a red herring to find out whether OP and her partner are behaving the same, on the same page, or not.

Great dp now the bills can be split 3 ways..
If he doesn't agree to this call the whole thing off..

I would pull out. You can continue as you are.

Have you sold your home yet?

This, and: what is his fabulous new idea for 'how you make the bedrooms work'?

Boxer321 beat me to it, I’m struggling to believe that your DP has only just found out about this

Also agree with everyone who is saying the son is thinking “Great, I can move in there and get her to do everything for me cos Mummy doesn’t want to anymore”

Keep your own house OP or you’ll be kicking yourself hard in a few months, or even weeks, of moving

Well, what is she moaning about? I must admit my son thinks I'm moaning a lot at the moment, because he has lofty ideas about which uni he wants to go to and the type of job he wants, but doesn't bother doing any work towards it despite A Levels being imminent! ! (He's almost 18.) Perhaps she just wants the best for him and he's reacting somehow? Which would just mean the problems will be in your house instead.

My husband’s son moved in with us. Similar ages. There were more college and work options, more freedom on offer. He cited nagging too.

I think sometimes that relationships get frayed. My own eldest moved out, likely because of a similar phenomenon (lockdown, too pent up). Perhaps it’s a natural thing that would, in the past, propel men to find their own way in the world. My son is doing fine now and we have a good relationship.

However, back to your stepson. If the nagging is due to said young man being a motivation-less and indebted slob, you’ve got your work cut out. Many parents assume positive habits like hygeine and helping out in the house develop ‘naturally’. Or they just endlessly pick up after their sons and then realise they’ve raised a man who thinks women are skivvies. From experience, it is possible to re-educate young men. If you’re facing this, you and your partner need to present as a team.

Now hang on DP, if we are going to cohabit together then we need to have discussions about big decisions like this. I'm not saying he can't but why are you just telling me as if I'm not part of the conversation.

If he apologies and admits that he was pleased and just didn't think then ok.

If he loses his temper and gets defensive / irate then hit pause on the moving in.

I would put exchange on hold until it's all discussed properly.

Don't exchange contracts before you have an agreement you are both happy with. This should have been discussed long ago. DP is assuming this is his house and he can do whatever he likes in it. That is the problem.

I'd be asking what his mother moans at him about in the first instance.

If it's his coming and going at odd hours, making a mess, leaving her to cook and clean...then he's not magically going to change his ideas if he moves house.

Saying that, I'd have gone ballastic at the initial conversation, as I spent many years in shared housing and it's not something I'd want to go back to, family or not...

This

Edit, I replied to wrong quote.

Well I think it is a red herring as OP has given no indication whatsoever she was thinking the same thing.

I suspect I’m being unreasonable here

If you genuinely think your reaction is unreasonable then I'm afraid that you may be in an abusive controlling relations without realising it.

What you describe is absolutely outrageous.

Another adult who you weren’t expecting to share your new home with - and what about cooking, cleaning, laundry etc, not to mention financial contribution. This all has to be discussed and agreed upon. I would be very unhappy to have this thrust upon me, as a fait accompli, like I had no say in what happens in my own home,

That’s just sneaky slipping it in like that.
Did he even ask you if it’s okay?
You’re going to go from living alone to sharing a house with two men and paying for the privilege.
I would be dropping out of the house purchase and putting moving in on hold until further discussions are had.

He’s a rubbish partner and example of respect to women to his son not to have said “I will need to discuss this with maximusss, it’s her house too”

Carry on living separately.

You've only had experience of living with your DP when his son stays 1 day a week, the dynamics will completely change when he’s there full time.

Yes it’s definitely his parents responsibility to house their child if the child can’t afford to house themselves (and let’s face it, few 19yr olds can) his mum has done her fair share and it’s time for dad to step up.

BUT, this doesn’t mean you have to live with him.

I can only imagine that the type of “nagging” this 19yr old boy is trying to avoid is things like “clean your bedroom”, “wash your sheets”, “pick up after yourself” etc. And if his mum, who no doubt loves him unconditionally, has got to the end of her tether with him, it’s unlikely he’s going to be the perfect housemate to you.

You’ve got a great set up at the moment; you have a home for you and your DC, your DP has one for him and his DS; why change that?

If you read my follow up posts, in conversation with OP, I was trying to find out whether they were both assuming their DC were welcome, whether plans had been made for one but not the other and whether OP was miffed about her partner assuming his child could live with them while she was doing the same.

I've also said it would annoy me if something was dropped on me with no prior discussion or agreement. And that all of these things should have been discussed before purchasing a house together.