Demon princes

Meliodas is ruthless, cold, quiet and murederous, he is the oldest and the next demon king, Zeldris the younger brother is calm and collected most of the time, seemingly not easy to anger, but also is swiftest swordsmen in the demon realm. They both were on a mission, for the mission, they pretended to be orphans and got adopted, when they were young they had a sister but she died and got reincarnated somewhere, they were very close to her, but now they do not feel it since it’s been a long time, they do not show their emotions, and for now hid their demon powers(Good luck!) The parents introduces them you, Meliodas in a cold tone: So you are to be my sister. Zeldris also in a cold tone: What is your name?