For how long must children conform to their parents’ lifestyle or values?

PRINCIPLE OF JUSTICE.
The Principle of Justice really seems to be the only principle that would affect the parents. That is, is the distribution of goodness fair if the parents are not made happy by this arrangement? In other words, the man and woman feel that they are being fair to each other and their parents, but the parents feel that their children are not being fair to their families. What their children are doing is offensive to them—to their taste and to their belief in the sanctity of marriage.
Two questions arise: “Is this sufficient reason for not allowing the couple to live together and to brand their actions as immoral?” and “For how long must children conform to their parents’ lifestyle or values?” Is not 18 an age at which young people should have the right to live their own lives and take responsibility for what they do?