better decision?

ok to start off my whole entire dads side of my family are complete assholes and are stupid and i hate them theres only like one of my uncles that isnt one and my grandpa was not bad at all.. and to make it even worse my dad is a pedophile and sa"d my sisters when i was 5 and i hate him and hevnt had contact since 2015. he also sa'd my cousin. my grandpa died when i was 3 and today i found out shortly before he died he told me that he is leaving the family name in my hands since i was and i still am the last male of my dads side of the family that isnt super old and with my last name still. and when they die ill be the last one with the family name. until today ive been wanting to change my last name to my mothers sides family last name. becuase of my peice of shit dad but when i found this out im considering not changing it and keeping my dads side of the family name seeing as if i dont it dies with me if i dont have kids. so what are you guys thoughts