What should I do for the best?

I think you’re getting an unfair bashing here, OP. This isn’t some stranger, you’ve been together 6 YEARS. Lots of the posters will be married and will imagine that should they be single they would never meet anyone ever again.
My mum met someone when I was 16, they married when I was 21. I lived in my mums house and she moved into his, would that be a long term option?

Liking someone isn’t the same as being ok with them moving into your home! Surely you know people you like but can understand this doesn’t mean you’d be comfortable to live with them?

Even while she is at uni it is still her home. If anything during that transition is when young people need to know that home is their stable and secure base to come back to. She will likely still be back for 1/3 of the year, at least.

All of your reasons for doing this are because it’s what you want. You say you put your children first but aren’t doing so. They’ve clearly had disrupted and traumatic family experiences and their home with you had been their one safe space and now you want an unrelated man to move into it which will completely change the dynamic and obviously be uncomfortable and unwelcome. Would you want one of your children’s partners moving in with you?

If joint holidays etc work, and clearly your relationship has been fine for years while living separately, then keep doing that. Don’t force an unrelated adult into your children’s home against their wishes. You will likely destroy your relationship with her if you ignore what she’s said and do this anyway.

I really don’t understand why you would prioritise living with a man over your children’s happiness, especially during such a crucial stage of development where to become independent adults they need to feel really secure with their family and home and that this safety net is there, not that you’re trying to change everything as soon as she is away for some of the time. It gives the impression that you planned all of this and have just been waiting until you can get rid of her, that you don’t really consider it her home too, at a time when she most needs to feel secure and wanted and missed so that she can spreads her wings with that safety net there if she needs it.

This is really toxic, especially the timing of it which seems very deliberate and of which I am sure she will be acutely aware. If you proceed with this I doubt your relationship with her will ever recover. Why can’t you just wait 5 years and move in with him then if you still want to do so?

I wouldn’t move him in in these circumstances both for your daughter’s sake but also because I suspect your relationship won’t survive it. She’ll be foul to him and it sounds like she’s already quite fragile mentally. I think there is little to no chance of her suddenly coming down one morning and changing her mind- I suspect she’ll get worse rather than better.

I would honestly wait another year or two until she’s more stable. If she’s 20, about to finish uni and should be starting to find her own way I would feel differently but not at this age.

It sounds to me like because of the difficulties with her dad she sees your house as her safe place and is very upset/ anxious about this being compromised by your partner and his kids moving in. I can see her point too- it’s a massive change and even if you do like someone then you don’t necessarily want to see them day in day out. I know for a fact I’d have hated it at that age, however nice the man.

Wait until she leaves home- or at least another few years.

Did you sit down and have a conversation with her about him moving in?
About why you would like him to move ect and her feelings?

I wouldn’t tell your dp your dd doesn’t want him to move in. I would explain to your dp she’s struggling and you don’t think it’s fair to disrupt her life further right now and you will re visit it in a year.

So all the benefits for your daughter will be materialistic. Nothing will benefit her welfare. Gotcha.

You've decided to bring some random man that she had no choice about, into her home permanently. She will have no refuge because her dad is not fit to parent. If I was her, I'd be angry and hurt too. You are effectively saying that her feelings don't count. That you care more about some man who already has a comfortable home, than you do about her, who will not.

Could you not wait until her a'levels are out of the way and she can spend most of her time at university?

I have a 17yo ds and am waiting until September when ds will be absent and I can date openly without harming our relationship.

Your DP has it cushy. Selling his home so he and his DC move into yours whilst he has the proceeds of the sale. What do you get out of it ?

There is a big difference between mum's boyfriend staying over (although you say that's when they should/would be at their dad's, so even with them not seeing that much of their dad over the last 6 months, is that really that often?) and mum's boyfriend moving in.

I'm generally not an advocate of letting teens rule the roost - I'm the adult here - but your daughter is obviously not comfortable with this and I get the feeling that it's not just to stamp her authority on the situation. It sounds like she has had quite an unsettled relationship with her dad which, added to GCSE year stress, will not be easy. This sounds like it will be a massive shift for her and raising it while she has all of this ongoing was probably not the best plan.

The fact that she likes him doesn't mean she wants him in her space all the time - it would mean taking away her comfort and safety.

You absolutely deserve to be happy, and have a life outside your kids, especially as it looks like she will be moving on in a couple of years for university. I agree with PP that if you do go ahead with this, moving him into your shared space isn't the way to go - you need to look for something that accommodates everyone.

And financial reasons are not the best reason to push this forward (just as an aside)

So the wedding is summer 2027? Honestly, I would wait and see how things are in a year or so. A year is a long time when you’re 16. I would also suggest the partner move in (if your DD is on board with it by then) with his own house rented out to begin with.

If she doesn’t come round, I wouldn’t force it. She’s at a really vulnerable age.

How condescending. Why cringe that someone is getting married , they're together 6 years!! Are you some sort of weird prude?

my DD is almost 18 and I definitely would not have moved anyone in when she was 16. Yes it is hard having to sacrifice relationships etc, but i’d be waiting until she is 18. Not least because she has made it clear she doesn’t want this. I know that’s hard on you, but I personally could not go ahead now she has voiced her concern.

I cringed when I saw you were getting married. You need to put the brakes on. Your kids need you. They’re dealing with a lot and probably need conselling. It’s a recipe for disaster moving a dp and his dd in. Your kids are nearly adults. Wait a few years.

Having him move in when she's expressed how much she doesn't wave that, would be unfair to him and his DD.

I know that 6 years is a good while and you haven't rushed into the decision, but no good will come off it.

Is she on a pathway to go to university at 18? If so, I'd leave it till then.

I also think a buying a new home is better, as she won't see it as her space being invaded and your fiance will also see it as a new home for both of you.

I empathise with how challenging this must be for you.

I'm surprised at the previous responses tbh. You are getting married next year having been together 6 years and people are saying you shouldn't be living together?! You can't have a 16 year old dictating everything. Your house, your rules. It seems you have been very fair to your dd all along. Now is the time to put the foot down.

For me it depends on whether she wants to leave home at 18. If she is 16, then you know what sort of path she is on? Is he heading down the uni route? Or will she need more time at home?

If she is very likely to leave home in around 2 years then personally I would think that is a good compromise for a family to make. 2 years is nothing, especially as that time includes selling a house, which can take a while.

I would say to her that you understand, and will start the process next year, aiming for him to move permanently after she leaves home. If she is reasonable then that should be very appreciated, and quite meaningful that her mum is obviously putting her first.