He hardly see his parents even when they stay for 3 months? That’s a lot of time.
Personally... this is going to ruin your marriage in due course. You are forced to put up with a situation at home with no regard for how you feel and that is not on at all, this is your home too and three months stats are unbearably long when you don’t get along with the visitors.
I understand that in some cultures (or some socio economic strata) it is seen as normal for the family to visit for months on end but I can assure you that that’s not set on stone. I come from one of those cultures but I am aware that we’re a lot of my friends have family expecting them to put them up for months, my parents and their friends wouldn’t entertain more than a week, as my father says “the visits as the corpses stink after 3 days.
My inlaws didn’t visit for 3 months, just for a week... six or seven times a year. We were at each other necks by the 4 day, with the ILs fed up with me doing things “differently”, I feeling like I could kill my husband for allowing them to treat me like that and him caught up in the middle.
Eventually things boiled up to a big argument from which we never recovered. We stopped staying in each other’s houses, the ILs hate me for that, but the worst part was that that precise argument ended my marriage. I was never able to see my husband other than as a stupid mummy’s boy with no guts whatsoever after it.
I left him as soon as I got a job and some savings to start on my own with DS.
Your h needs to get his head out of the sand before he ruins his marriage, because believe me, the inlaws are not the problem, your husband is.