to think this CAN work - son and pregnant daughter-in-law moving in

So the notice was served, they turned down your offer of living with them for a few months, but then in that time-knowing they were going to be made homeless from
their bedsit, got pregnant?

I'm in a similar situation and so far, things are OK. My daughter and son in law moved back from Turkey about three weeks ago because my daughter has a new job in the UK. My son in law has also found a new job in Germany and once his visa has been approved, will be there during the week and then he will either come here for weekends or my daughter will go there. In the meantime he is working from home here.

I've worked from home for many years but am starting to reduce my hours now thst I'm retirement age, and so have rearranged my home office as a bedroom for my daughter and son in law, with a sofa and a smaller desk. My daughter has always been really awful with keeping her room and the rest of the house clean and tidy but so far, things are very different. They are being respectful of our house and the kitchen in particular. They have their own shelf in both of our fridges and I have emptied out a mini freezer that I bought at the start of the pandemic for them. I've made some cupboard space in the kitchen as well.

Food isn't an issue as they are both Muslims and only eat organic food, so most of the time they are buying and cooking their own food. The only slight issue is the bathroom; we only have one bathroom and a separate second toilet, but in the mornings they are both fine and leave us to use the bathroom before they go in. Bedtime can be a bit more difficult because they both spend hours in the toilet before bed, and I do get irritated when I can't get into the bathroom when I want to go to bed at 1, but nkw thst my daughter is about to start her new job, I assume she will be going to bed earlier.

They have also been extremely quiet when they've been getting up in the small hours to pray and to eat before it gets light during Ramadan. They are doing their own washing and cleaning.

I was a bit worried before they arrived but so far, there have been no major issues. My son in law in particular is very concerned about us not doing too much in the garden and outside and seems to think that we are unable to do things any more becasue we are in our 60s, which can be irritating, but it's meant in a good way.

I'm not finding the thought of the next year is filing me with dread and although my husband and I have enjoyed having the house to ourselves for many years now, it's nice to have the company. It's not really costing us anything extra to have them here, apart from the cost of the new bed, bedding, and towels thst I bought. I realise that it will be very different for the OP having to contend with a baby as well, but I think it could well be doable.

Set clear boundaries and expectations.
You should definitely charge rent, if you don't want to keep it then save it up and give it back to them. If it all goes wrong they can use it as a rental deposit!
Don't under estimate how stressful it can be.

I think many of us are going to have to get used to a switch back to multigenerational living and I don’t think the idea is a bad one in principle but I’m afraid I think this part is utterly mad. As multiple pp have said, this arrangement is not going to last a year and is likely to go on much longer. You are going to relegate yourself to a bed sit in your own home. Where will you entertain your friends? What happens if you meet someone?

That’s what I was going to ask. Was it a no fault
eviction (landlord selling etc) or they didn’t pay their way. The latter would worrying me moving into my home, especially with a baby on the way and DiL going on Maternity leave

Communication is key! It's worth discussing in detail to ensure that expectations are aligned. For example, you all agree to keep the house tidy. But one person's tidy might be completely different from another person's. So really discuss in detail the things that are likely to become problems. In my experience of sharing houses with others, cleaning, tidying, cooking/meals, use of shared spaces, laundry, and noise have been the big issues.

It might be helpful to have a few 'house meetings' in the first couple of months, just so any emerging issues can be talked through.

Also if you're cooking and eating separately, it would be nice to have a meal together once a week, maybe a relaxed Sunday dinner. You all will be living together so I don't think you should have to pretend you don't exist/stick to your room. Eating together is really bonding and if you're not spending lots of time together in the week, just passing by, then it will be a good chance to reconnect and have some fun together.

From someone who has had to rent my entire children’s life.

thank you for attempting to give them this leg up.

@dirtyblond are your other dc aware this one/wife/baby are moving in rent free for potentially an extended period of time? I know you've said they're all settled and have bought their own places - did they have help from you to do that or is it just this one? If not, have you/would you consider reducing this child's share of your property in your will by a fraction to make it more equal between all your dc? Assuming it would be going to them at all.

I'm guessing he's the favourite youngest?

Where are her parents in all of this?

@dirtyblond I agree with this poster. Your boundaries could get blurred with time. Just don’t go there. They will end up taking over.

No chance council will house them on professional salaries. Best they could hope for would be help finding a private let.

I've done this (not with a baby though) and it worked OK. I also had a large bedroom I could use as my sitting room /study.

We had lunch and evening meals together, taking in turns to cook and this worked well for us, especially as I'm a rubbish cook so they willingly took my turn over! For me, it was bliss having my meals cooked. We agreed a cleaning rota, which I ended up doing more of in lieu of the cooking and I did a weekly shop online.

Communication is the most important thing so that resentments don't build up eg my son kept overfilling the washing machine and we had several 'words' about it. It's easy to slip back into a Mum/son groove where Mum knows best but an adult son will resent it, especially in front of his partner. I also avoided them when they were having an argument with each other!

They were here for about a year and overall, it worked well as we're all fairly tolerant people who can laugh at each other's foibles. I have no idea what it would have been like with a baby in the mix but I imagine I'd have done more eg their laundry and also been aware that they'd have been more grumpy due to being sleep deprived.

‘Responsible for one man’? Are you a time-traveller?

They will not get rehoused in London, especially with good salarie. They’ll be sent towards the private sector which frankly is only right.

Both full time but can't afford mortgage (presumably they have been actively saving for a while), can't afford rent. Reckon they can save enough money within 12 months to make a difference. Unlikely.
Lots of baby things to buy which is expensive. Although a lot can be bought 2nd hand.

Do they have a savings plan? Have they estimated costs?

Before my DH and I bought our house we did a plan and to the best of our ability built in a buffer. We included periods where I would have low or no income due to DC. We knew we'd be alright (aside from any massive unforeseen issues, but we did have backup savings for that)

Oh sorry I see you're in London and I guess you're right that would take years even with high priority.

Sorry when I say "no right" I just mean that the council or anyone can't challenge your letter and demand you let them stay.

Haven't RTFT so sorry if this has been mentioned, but I'm just commenting on your DC and partner's circumstances.

If they live with you and can't afford to rent privately, the best thing you can do for them is write them a letter with notice saying they can't live with you.

They have no right to be there and your council will need to house them. Obviously they will need to genuinely not be able to afford to rent, but they do understand this happens and will have a duty to house.

Well they don't sound very sensible having a baby when they don't have somewhere to live.

Was the baby planned or an "accident"? As others have said, they are almost certainly going to be with you a lot lot longer than a year and then will be having another baby.