@phil777 my fathe and our family live in small house with my grandparents and cousin and I have relatives who have three extended family living in one residence, even I'm still living with my parents well i do pay the half the bills I'm just waiting for my mother to start getting her pension and I'm out two more years. By the in the extreme cases there are up to 5 or more extended family living in one residence. here a read on how extended family is structured.
https://www.livinginthephilippines.com/culture-and-people/philippine-culture/1308-family-structure
https://culturalatlas.sbs.com.au/filipino-culture/filipino-culture-family
https://culturalatlas.sbs.com.au/indonesian-culture/indonesian-culture-family
https://culturalatlas.sbs.com.au/malaysian-culture/malaysian-culture-family
So in other word in SEA countries the nuclear family is the norm don't know about Japan.