base on what we get in this link : https://onepiece.fandom.com/wiki/Haki/Haoshoku_Haki,
CoC can be heritable from Father to Son ( Garp,Dragon (unknown yet),Luffy) - (Kaidou,Yamato) - (Roger,Ace),.... like people has more than 0,0000001% to get coc but if their parent had strong coc's genetic...