I remember reading this series where the main girl falls for someone with a power, I can't remember what kind exactly. Anyway he ends up leaving her cause he thinks he's bad for her or something and moves in with his uncle. She is left with kinda a very weak version of it and he ends up coming back later with a female cousin who also has similar power.
It starts out in high school too.

Can anyone help? I know my description isn't the best...