To want to kick out DS of the house

Make it clear for him, write this on paper with a deadline of 48h to read and consider:

1. Move out within 3 months
2. Live at home and clean up after using every space across the house. Tick option, sign here............

I appreciate his age but has he ever been helpful, clean and tidy at home?

Has he ever been shown how to organise a cleanup? (and don't all come after me - his ASD may prevent him working it out. Doesn't mean he can't learn)

Every one keeps mentioning a cleaner - would any cleaner want the job of rotting foodstuffs all over the place? And what happens in the kitchen the other six days?

Is DH helping to clean up after his son? Because if he isn't that explains his "OP is too harsh". Either DS or DH cleans it up. Be firm.

However you have mentioned other children getting stressed by it all and I assume they are younger. One person impacting negatively on others is not fair at all and he either needs to buck his ideas up or he needs to move out. Give him one month to decide, then it's time for some tough love.

This. ASD is no excuse for squalor and filth

Chuck him out or he pays for a cleaner. He's 23 ffs not 10 🙄

I think making him pay for a cleaner is the answer.

Some people are naturally messy and disorganised, for whatever reason that is, personality or neuro diversity. But if he's sharing a space and he doesn't want to clean it, he'll have to make financial reparations.

I agree. I've known some really scummy people who move to their own house and suddenly become really house proud. OP, 23 with a good job is time to move out.

In my experience you only really learn about cleanliness and finances etc when you move out. He's 23 with a FT job so it's time to go. He can get some real life experience (and if he ever moves back if needed for stints in the future, he'll have learnt to be a better-functioning adult so will be more pleasant to have around).

Third or fourth-ing the cleaner suggestion. He may well lack the executive function - spoons theory; holding down a demanding job can make it less easy for an autistic person to cope with home duties on top, and not less - but if he's earning well he can afford to outsource it to someone paid to do it, and not dump it on you.

DH is also very annoyed but thinks I am too harsh.

Does he help clean up after him or does he leave that job for you?

This.

My son was like this in his bedroom
Kitchen wasn’t so bad as he didn’t cook much
but his bedroom he could have a dead body in there and I wouldn’t have known

I had a rule ( keep the fucking bedroom door shut )
And my other half fixed the window so it had to stay partially open ( so fresh air ) but if he wanted to live like a slob as long as I couldn’t see or smell it that’s down to him

strangely he moved out in to rented around 2 years ago and then bought a place with his partner

both places you could eat off the floor
always smelt lovely like pumpkins or fresh bread😂

I have never been in his house and seen it messy
mirrors always polished
floors are always swept and vacuumed
kitchen and counters are always clean
fridge always clean and tidy
rarely dishes that need washing

The bedrooms have no dead bodies hiding in them
bathroom toilets are clean and bleached

it’s not his partner cleaning up behind him either as he says how nice and tidy my son is 😂😂

I would make a very clear written list of expectations and then go through it with him, giving him 1 month to follow it otherwise he will need to move into his own space.

I think you need to realise that just because he’s intelligent and has a good degree it means only that. It’s no reflection on his ability to keep house. Also I think if you stopped think about his autism as mild you might get somewhere with him.

Do you have an awareness about ‘executive function’.

OP you've told us about his behaviour, which sounds awful. What's his attitude like? Is he rude and dismissive or does he get upset and say he can't cope?

For me the attitude would shape my reaction more than the filth.

I be blunt and very blunt with him.

What i would say is.
You want to live like a pig find somewhere else to live like it because your not staying here living like that end of.
So you either change and start living like a human or get the fuck out start looking for somewhere else you got one month from to day.
Find somewhere else or clean up like the rest of us and no im not joking.
Welcome to the adult world.
Ending with this -- > Cup a tea anyone.

Sometimes we have to be harsh for the message to get through even tho we dont want to say things that may hurt.
But there comes a time when enough is enough and the molly cuddling and sweet talk stops.

@PoliteExpert he keeps it nice when there's no one else to do it for him.

By not clearly setting out and holding him to account on basic standards of cleanliness you and DH doing him a disservice. Your DH may think it's harsh but what's the alternative? He moves out to a houseshare or to live with a partner, continues to live like a slob and inflicts this on someone else. If they're not related to him, chances are they'll be a lot more blunt and a lot less patient...

I'd set out some clear expectations and tell him that if it isn't something he thinks he can manage for whatever reason then he needs to consider hiring a cleaner at least for his personal spaces or start looking for his own home/flat/room somewhere so he can live how he wishes.

what state is he living in?

We were in the same position son was 23 asd messy and never listened and was coming between dh and I and annoying his siblings so we gave him one month and it was the making of him.
Our relationship is so much better because as much as we love him we just couldn't live with him but now we have a mutual respect.
You're not doing him any favours and if he's outstayed his welcome he will come between you and dh.
Ds has a little studio flat and is loving his independence and we're just round the corner if he need us.

1). Did he ever have the skills to tidy up after himself and has he regressed? As a pp suggested, he may be functioning at capacity.

2). Has he always been messy? Will he always need a well paid cleaner/housekeeper type? Then suggest he needs to start paying for one. Might as well work it into his budget early.

3). Did he move away for university and how did he cope? Did he have support and what form did that take?

4). You have posted in AIBU so may get some harsh answers. Might https://www.mumsnet.com/talk/special_needs_teens_and_young_adults get you some more targetted responses?

No medication for ASD.