Beautiful drawing! These two are my favorite dbz characters. They are villains, but they have a cool personality (except in the Trunks' future) and are just teenagers who want to have fun. The other dbz villains are so superficial and lacks personality (except vegeta, but I don't like him).
The twins, abducted by Dr. Gero. They have forgotten their past, because of Gero's experiments. They can't remember their past, but they remember what he did. Their hatred for the doctor is what allowed them to keep their individuality, and rediscover what it means to be human.