Grandpa appears ........ to be of sketchy mental health ........ in his mugshot. This could be the only way mom has ever lived.
I agree. I'm thinking a scenario like this: Generation 1 has OCD/hoarding, which grows gradually worse as he ages and possibly loses his wife. Generation 2 grows up in this environment, knowing it's not particularly normal but also growing used to it simply because humans can get used to anything. When she has a child, the child is born into the same situation.
It can be extremely difficult to find help for family members with this disorder, especially since in many cases they are unwilling to get help, and in their generation it is considered shameful and an admission of weakness to get mental health treatment, rather than a useful service that can help you avoid a lot of pain and hassle, as younger generations tend to see it. For a while, they can say, it's not too bad; things aren't so bad that I have to stage an intervention--but then once it gets bad enough that it's an obvious problem, they start wondering--will they take my child? My animals? Will I lose my home?
It's a situation that can trap the people living in it. Maybe this family was lucky--no one died or got seriously hurt before they were pulled out of it. It'll be bad enough when they realize what the child has had to go through (I'm assuming they care about the child--mental illness doesn't stop one from caring, after all). Imagine how much worse it would have been if the child had been hurt. They would never have forgiven themselves. It's going to be hard enough for them with the likely fate of at least some of the animals being to end up at a shelter and be euthanized due to disease or simply being shy adults in a world with too many unwanted pets.
Perhaps the father can care for the child while the rest of the family gets some kind of help... Grandpa might need residential care, if he's the one with the major issues, but this kind of thing runs in families, and Mom is going to be seriously prone to developing a hoarding problem of her own.
'course, I could be completely wrong here, I'm just speculating based on what's in the article; I haven't interviewed them, and I'm not a psychologist (yet) in the first place.