http://www.mangago.zone/read-manga/royal_servant/uu/royal_servant-chapter-20/
http://www.mangago.zone/read-manga/royal_servant/uu/royal_servant-chapter-22/1/
His mother (presumably) was killed by his father via a liquor bottle, and then his father sold him off to a slave market when funds were diminishing; When Sihan encountered Ryan, he requested that Ryan turn him into a royal blood. Ryan gave Sihan some of his powers to induce a mutation in Sihan, from a servant to a royal blood, without the need for a core. Sihan survived the painful mutation, didn’t die from it and developed a core, completing his transformation into a royal blood~

I'm a bit confused about Sihan's past. How come both his parents are human/servants and he is of royal blood/aristocrat? I think I missed something or didn't pay proper attention. Help lol.