Roxanne and Dominque Weasley

So I am just going to upload anything I sketch when I am bored and I drew these two the other day...

I think, in my head, they are the same-ish age but they are totally different. They get on, and they hang out together, but only at family occasions. At hogwarts they usually go their separate ways. One thing they do both care about is being different, look and attitude.

Dominque is a rock chick with an apathetic attitude
Roxanne is a sassy, speaks her mind Amazon woman. (She is very tall for her age, and strong. She is younger than Dom)

Hope you enjoy...
Was wondering, I feel like my drawing are flat and bland, anyone know how I could make them become more alive?