Can you clarify just how distant you mean by progeny? At this point Karl Marx’s descendants include great-great grandchildren who are obscure and distant enough to be relatively unknown to the academic world. One interesting case was Marx’s great-grandson was Robert-Jean Longuet, who infamously rebuffed French Communist advances by claiming that they had “falsified” his great-grandfather. A New Yorker profile of Robert-Jean in 1954 further claimed that none of Marx’s 13 living descendants were members of the Communist party or politically active. Yet two of his great-great-granddaughters, Frédérique and Anne, have taken the last name “Longuet-Marx,” emphasizing the connection.