I did this because his dad thinks masturbation is bad, and I didn't want him to think that. Also, I didn't want him to be scared the first time he ejaculated. I just gave him a basic definition – no techniques – and I gave him the address of this site. I haven't seen anything in the Bible that says masturbation is wrong, anyway. (We both believe in the Bible.) Have I overstepped my boundaries or done something illegal?
I don't think you did anything wrong, and you certainly haven't done anything illegal. In fact, it's great that you were sharing good, healthy, well-intentioned information with your cousin, and I'm sure he'll appreciate it later on. As for the Bible...well, many Christians believe the story of Onan (Genesis 38), who spilled his seed upon the ground, condemns masturbation – but it's definitely a matter of interpretation.