Noun
red diaper baby (plural red diaper babies)
(chiefly US) A child of parents who belonged to a communist party (usually the United States Communist Party) or supported communist ideas and goals.
A person born to and raised by a member of or supportive of the Communist Party USA.
A person born to and raised by a parent or parents who held any radical political views.
Source: en.wiktionary.orgred-diaper baby