Adultery -

…However, there was discrimination against legitimate children in the succession of titles and the family's religious rights. Furthermore, children born without legal marriage were called illegitimate children, and were called "bastards" or "bastards born to concubines." Thirdly, those who were responsible for teaching and admonishing the children of feudal lords and nobles were called "bastards."…

*Some of the terminology explanations that mention "kansei" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…しかし封爵や家の祭祀権の承継では嫡庶に差別があった。なお適法な婚姻に基づかず出生した子はいわゆる私生子で，姦生，婢生子と呼ばれた。第3に諸侯卿大夫の子どもに対して教え戒める役目の者を庶子という。…

※「姦生」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報