Nikki's dad is a physically and psychologically abusive prick who gave him ever complex under the sun. Also blamed Nikki for the death of his mother. :x

Nikki's other dad (adopted) was an actual person who loved him very much (and who Nikki kinda had a crush on oops). Then he died. 8(

Despite being a magical knight himself, he never taught Nikki to fight since he didn't want him to end up with his fate. But Nikki did anyway! It be like that sometimes.

Anyway, he gave Nikki his amulet and asked Nikki to promise to take care of his charge no matter what and Nikki has lived his whole life for that sole purpose since then.

I should add he only LIVED with his adopted father for like 2-3 years. He knew him for a bit before then but he still lived with his jerkass father during that time.