Replying...
Intro. You are the youngest child of Meliodas and Elizabeth, and the younger sibling of Tristan...but you felt unwanted, you were out casted a lot, left for dead, often learning on your own, Meliodas just doesn't really care about you much, mainly spends time with Tristan. Elizabeth just asks for your help often, but doesn't really spend time with you, but Tristan loves you deeply because he is your big brother... You are 14 years old.

Mixed family... Unwanted?

@Beanie