Why did some fathers and sons in ancient Japan have different surnames? For example, the father's surname is Takakura, but the son's surname is Hasegawa, Kubota, Sasuke, Takashi and so on.

In ancient Japan, the reasons why the surnames of fathers and sons may be different mainly include the following possibilities:

1. Adoption or adoption: Sometimes, wealthy families may adopt or adopt children from other families to inherit family property or status. These children usually inherit the surname of their adoptive father or stepfather, not the surname of their biological father.

2. Inheritance right: In some feudal societies, only the eldest son can inherit the father's surname and identity. If the second son or daughter of a family wants to inherit family property or status, they usually need to change their surnames to show their relationship with the family.

3. Marriage: In ancient Japan, marriage was a common form of political alliance. If members of one family marry members of other families, their surnames may be changed to show their connection with the new family.

4. Special status: Some Japanese families may have special status or power, such as royalty or nobility. Members of these families may use surnames different from those of other families to show their special status.

In short, some fathers and sons in ancient Japan had different surnames, which may be due to adoption, inheritance, marriage or special status. All these situations help to explain why different members of a family may use different surnames.