In Japan, the family register system is used to record the relationship between family members. It also acts as a record of all births, deaths, marriages and divorces and plays an important role in determining heirs in probate matters. Official copies of a family register are required for many legal procedures in Japan.
The family register is generally organized based on a single parent/child unit and families are usually categorized under a single family name. Therefore, families that divorce do not fit neatly into the family structure assumed by the family register. Furthermore, children of divorced parents and the custody of such children also does not fit clearly into this format.
To fix this problem, children’s entries in a family register will have a section for the child’s legal guardian. As Japan generally only recognizes sole custody, the guardian of the child will be limited to one parent after a divorce. For children of divorced parents, the parent with sole custody will be listed next to the child’s entry in the family registry. This allows the family registry to be used as proof of custody of children as well.
However, because the family registry is intended to include information on all family ties, a parent who does not have custody of his or her child will still be listed in the child’s entry in the family registry. This allows the family register to continue to be used as proof of parentage, even if the parent no longer has custody of the child.