Concerns for unhygienic state of the home my Grandson lives in.

Agree with others , your son is just as responsible. You have a good relationship with them say nothing.

Dear me, this post has sent me into a cleaning fit. You need to speak to your son as discreetly as possible. Mould on the curtains and windows is very unhealthy and can cause asthma in people. I know everyone's cleaning standards are different but this sounds awful. Wishing you all the best with this.

For me the cats present the worst problem, and probably lead to a lot of the others.

Does a health visitor come at all?
Presumably, not for a long time given the current situation.

There is precious little you can do, it seems to me.
Perhaps speak to your son and explain (supported with a leaflet maybe?)its imperative to keep the cat litter trays empty and clean, for his sons sake.
Cat faeces are very hazardous to young children.

I would emphasise what others say. Your son is just as responsible for looking after the house as his wife. What is he doing while she is looking after the baby.

In most households these days chores are shared between partners as is housework.

Speak to him about it and question how he feels and what he is doing about it.

Why aren't you mentioning this to your son?

Why are the cats all kept indoors? If they were allowed out some of the time, it would alleviate the need for 6 litter trays, and would cut down on some of the mess.

How very difficult for you. If it were just the adults I'd say let them get on with it but I'm sure you're mostly concerned for your little grandson and rightly so. His health is at risk and it will be impossible for him to have friends around when he’s older. However, once a person gets used to that level of dirt then they simply don't see it. I’m sure lockdown hasn’t helped either. You're on a losing battle in many ways because of the cats and the litter trays etc. If they want to keep so many cats then that's their choice unfortunately.

You seem to have a good relationship with his mother, so hopefully you can discuss it tactfully. It's all about the way you approach it and you'd have to be very clever in how you give her an understanding of the dangers of such poor hygiene but without getting her back up! Very tricky. They will not be able to deal with that level of filth on their own and it should be done professionally. So if you can afford it maybe you could suggest you pay for a professional deep clean, and then have cleaners come in weekly. You could say ‘I realise how difficult it must be with five cats, I’m sure I would have a cleaner in weekly myself.’

If you sense she is getting annoyed or upset at all then you must back off immediately, as you don’t want to compromise your relationship. You could then try a heart to heart chat with your son on his own, highlighting the health hazards and how his son will have difficulty forming friendships if his friends are not allowed to visit.

Peasblossom

Why do you think it’s just your DILs responsibility. If you really think it’s unsafe speak to you son and give him a list of his cleaning responsibilities.

He could be responsible for seeing to all the cat stuff. That would solve most of the problems.

I agree with this too. The cat waste is the most hazardous so if he deals with that?

does your GS get stomach bugs and so on?

Why do you think it’s just your DILs responsibility. If you really think it’s unsafe speak to you son and give him a list of his cleaning responsibilities.

He could be responsible for seeing to all the cat stuff. That would solve most of the problems.

I agree keep out of it but your son is equally responsible of course.

I suppose it depends if your son and daughter in law are happy to live like this, or if it's something that has got out of hand over time.
If it's the latter, you could perhaps offer to pay for a deep clean, or weekly cleaner for them?
If they're happy though, you will have to bite your tongue.
It does sound nasty though.

You could offer to pay for a cleaner once a week. Sounds as if she is inundated with work and a young child. What does your son have to say? After all he should be sharing the chores so it’s down to him as much as dil. They ( not she or he) need to be careful of hygiene with so many cats.

I understand your concerns but agree you should say nothing.

If either you son or DIL starts to clean up a bit while you are there, maybe you could offer to help but it would be terrible to damage your relationship with them.

I used to work as a support worker and tbh this situation isn't unusual unfortunately. Sometimes we would go and in help clean and make a cleaning rota but a lot of the time the situation would return to how it was previously. Some people just have different levels of normal. It's not something I am comfortable with but some people just don't see it. I don't know what you can do though really as you are related, you say get on well but do you get on well enough to say shall we have a bit of a spring clean one day, it might help if I take some stuff to the dump for you? Get it all ready for christmas?

As someone not related I tended to go in and just start 'helping' to tidy. I know in a couple of cases that meant the bags of stuff stopped happening. I'm not sure what it is with hoarding bags of things, it happens quite a lot. I've noticed someone in my family does it too.

I second grandmabatty's post.

You do nothing. It isn't your child or your house. What does your son do? It's equally his house so equally his dirt too. I say this kindly but mind your own business.