I am healthy and not overweight, why do I have cellulite?

I am very muscular and have been my whole life. I am only 15, but I guess age doesn't matter. I am athletic and have always done gymnastics and dance. Is cellulite a bad thing? I know what it is and all. Like I said, my legs are very muscular, so does that have anything to do with it? I've heard genetics plays a role in this too. Thanks!