1 minute ago, ldorn said:How about the late Doji Satsume? Either...
A. Shoju ordered Kachiko to sleep with Satsume so he could have an heir, then ordered Satsume killed.
B. Kachiko was infatuated with Satsume, Shoju found out and killed Satsume out of jealousy. When the child was born Shoju decided to keep him.
C. As B. but Kachiko ordered him killed, then presented the child as Shoju's.
This has possibilities.
The idea of Kachiko romancing both father and daughter is a little....icky.