Varicose and spider veins question?

my mom and aunt and grandmother have both of these types of veins and my mom said they are hereditary so i am bound to get them. i noticed a greenish dark spot on my thigh that hurts when i push on it, but idk if it is a bruise or a varicose vein because my moms veins pop out and she says they hurt. so are there anyways a can prevent them from getting any worse then they will already be when i am older? and what causes them? how old do you usually get them? i am 15