The traditional ideal of the "ie" system designates the oldest son as an heir to the family, and expects his family to live with his parents. When the oldest son is not available or not able to assume this position, one of the younger sons may do so. The elderly parents may opt for living with one of their married daughters, usually when they have no available son. Implied here is a sex/age hierarchy in terms of living with the parents, descending from oldest son to youngest son, and oldest to youngest daughter. It thus can be expected that oldest sons and oldest daughters without brothers are more likely to live with their parents than other children.