In my genealogical research, I have come to learn that in Europe, and in particular, the Czech Republic, the oldest son would inherit the family property and the parents would live there until they died. Once they came to America, it changed. In my family, the youngest son inherited in some instances, but the parents continued to live on the property until they died. This was until around 1900. It was built into the way life worked.
It is still like that in many parts of the world. I know some people, married and with children, whose parents live with them. In one situation, the parents are retired, but active. They drive and are involved in all kinds of activities. They have a bedroom on the first floor of the home while the grown children and their two children have bedrooms upstairs. I can see many benefits to this. I can also see potential problems with challenging personalities.