State of FIL house

Not sure there is much you can do sadly OP but I would try to get your FIL to allow you to take the dog to the vet for a check up. It doesn't sound like either he or the SIL is able to take care of the dog and she may well be suffering.

@ThroughTheRedDoor thank you for posting that link. That’s very useful guidance.

Social care don't have to accept private capacity assessments when it comes to funding services. They have to do their own.

You have tried OP but if he isn't receptive to help it's very difficult.I agree with contacting the council about the mice as that could escalate at pace if they have food to eat and places to nest. Would FIL be open to keeping all his treasures in one room do you think? That way they could be untouched but the rest of the house more hygienic.

My GP were like this- DM used to send Dsis and I round to visit. One of us would hide behind a bush and then sneak in with the flash wipes and stealth clean the bathroom and kitchen when the other one was talking to them in the sitting room. Fortunately they were both quite deaf so didn’t hear me but I did once have to hide in the boiler cupboard when they came in to make more tea. We laugh about it now but it was really stressful at the time. Honestly the house was awful but they just couldn’t “see” it.

My PIL are like this. We tried to help, they insisted the house was fine, nothing needed doing. In the end I said to DH he could go and see them but me and the children wouldn’t be going over until it wasn’t so dirty. It was a complete health hazard - mouldy plates, the dog had worms and used to rub his bum along the carpet etc. it stunk. It made the relationship very difficult, but they managed to get a cleaner. To add - they have plenty of money to do so.

The only thing you can do is contact adult social care and make a safeguarding report under self neglect. With a mild dementia diagnosis they will need to have him on their radar as his cognition will worsen over time and they should complete a capacity assessment. I had to do this for DAunt with similar issues. It is not a quick fix as if they have capacity they can refuse help which DAunt did. They can act on hoarding if it causes fire safety issues that would impact the safety of others, but it is not simple. They may also act on the pest control issue. DAunt at first agreed to allow a visit from the fire brigade and then refused it. I had to complete several safeguarding referrals as the situation rapidly worsened once she stopped eating and her cognition declined swiftly as a result. Social care repeatedly stated she had capacity. Her GP was useless. She ended up having a fall due to clutter in the home which resulted in admission to hospital, it was only then that the hospital doctors fully listened and declared her to not have the capacity to keep herself safe. She died in the hospital a few weeks later. If I had my time again I would get a private assessment of mental capacity completed by a professional rather than waiting for social care if the situation was deteriorating. This is what my neighbour did for her sister when she was unsafe at home (wandering with dementia) which enabled her to organise care for her DSis.

My DF who has COPD, is likely ND and now has dementia (as yet undiagnosed by memory team but a CT of his head showed obvious changes) is very resistant to all change in his home. Everything being where it should be allows him to map his world, fills gaps in his short term memory which enables him to feel like he knows what is going on and reduces his anxiety. Anxiety is massive when you are confused by the world around you due to changes in your cognition. He has been miles better since the GP started him on citalopram for anxiety around his breathing. Far less controlling about his environment allowing people to help with cleaning, helping him with his meals and self care which he neglected before. I find he listens to doctors more than me so if FIL listens to his GP it might be worth your DH speaking to them about his concerns.

I think all you can do is a referral to Adult Social Services. If they have mice, it is hard to get rid of an infestation if there is food around for them to get into and they multiply at an alarming rate!

Don’t get stressed about it, it’s not worth it. Let them live the way they want to, it’s not a reflection on you.
If you want to do something, refer to social services confidentially.

You’ve done your very best. You can’t do any more.

It doesn’t matter what other people think.

Have you seen the clutter image rating scale? For some reason I can't attach it here. But if you click the button on the link it takes you to a scale that helps identify how 'bad' the clutter is. Anything above a 4 they encourage people to get help for their hoarding. Where is the house on this scale @Hohofortherobbers ?

https://hoardingdisordersuk.org/clutter-image-ratings/

I have a family member like this. He's always going to 'sort it out' but never does. Won't accept any help. Only very reluctantly let's anyone in the house, on very rare occasions. I too think it will kill him one day.

I wouldn't worry about paramedics or anyone who has to come in to the home, they will have seen it all and more. You only have to browse this board to know how often it's not down to 'neglectful children '.
I do the occasional bit of cleaning if DM is incapacitated and/or something is very bad, otherwise I can't bang my head against that brick wall any more.

The mice sound bad.

First thing to do is to let go of worrying about what other people think. That will drive you mad.

Would he agree to a cleaner just for the bathroom and kitchen? That way the food prep, toilet and washing areas would at least be cleaner and they’ve got less likelihood of progressing to rats.

Just be open and blunt about the dust and its likely impact. Though I’m not sure the dust would make that much difference to his COPD would it? Mould might though.

It sounds as if they both may be neurodiverse tbh.

Paramedics won’t blame you for the state of the house, it’s a common issue. Elderly people with more than enough money for cleaners refusing to accept them. I wouldn’t be trying to do it yourself as from experience the chores will expand exponentially.

If it’s a health hazard I would consider putting in a report to social services, in fact because of the mice I would just go ahead and do that. The place is unsanitary and your DFILs living conditions need to be investigated.

Is it just the dust or is there mouldy food, clutter etc?

If he has ill health he must go to the Drs or hospital sometime? If you could get him to allow you to dust you could then buy an air purifier?