noun · a son born to a concubine or born out of wedlock; an illegitimate son

他在封建礼教下被视为孽子，地位远不如嫡出的兄弟。

noun · an unfilial, disobedient, or unworthy son who brings shame to his family

那个孽子竟然做出如此大逆不道的事情，真让家族蒙羞。