Family minimum unit
The words "family" whom Japanese people recognize are not all blood relationship persons.
When I got married, a family becomes only my wife and child. I do not call my parents' thing family, but say it as the my parents as a relative. When I get married, a brotherly thing is never called family. A brother does not have a relation on money and living together usually, when I get married. Many of a Japanese family view are it.
That is, marriage of Japanese people changes the range of a family.
With the family, it consists of unmarried children which made me and my wife a unit.
It is not that parents are not important. We appreciate for parents and we love own parents. We think it another thing to live in the same house together as that.
Parents release all her restraints, when their daughter gets married. A wife breaks off a relation with her family. It means that it is not not contacting but it belongs to a husband's blood relationship.
so, in Japan, when I get married, living together with my parents is not a city. Since the custom remains old in the country, in the country, a wife may live together with a husband's parents. A husband is the eldest son, The case of it becomes so. However, it is rare now.
We think that a family is the unit which the independent human being constitutes. And we think that marriage means independence.