No offense, but the fact is that I'm sure there are thousands and thousands of young siblings all over the U.S. who masturbate in front of each other. I find nothing wrong with it as it's the kids way of experimenting. All kids are curious and they experiment. Kids have parents, right? So how are kids made? They obviously get made from parents having sex. The kids know that their parents have sex all the time. So it gets the kids curious and they want to experiment with their siblings. Nothing wrong with it as long as it's legal and it's in your own private life. You just need to be responsible about it.
When I was a kid (about 10 years old long ago), me and my brother used to take baths together all the time. We didn't masturbate in front of each other, no way, but we were curious of what our naked bodies look like.
All kids experiment with sex and masturbation. I'm sure many many many of you in these boards had experiemented with sex and masturbation with siblings and relations in other families but you are too afraid and embarrassed to admit in these boards.
Hell, even rock star Jerry Lewis married his own cousin!!!