My brother (16M) and his friends have a secret sex symbol, what do I do?

Hi Reddit, looking for some advice here.

So my little brother is a very popular high schooler who is active in wrestling. He won states last year and has many friends through the sport. Him and his friends practice at a local wrestling club and are seen as leaders and role models in this club. He is asked to take photos with the young wrestlers all the time since he won states, and is seen a local celebrity in the wrestling community.

This is where it gets weird. Recently, him and his wrestling buddies have created this hand signal that they use while having sex (it kinda looks like the rock and roll sign). Not only do they do this, but they record themselves making this signal while having sex and showing these videos to each other. They call the signal “she masting”, and in order to be “inducted” to their group, you must record yourself holding up this hand signal while having sex and showing that video to the group. As of now, I know of 6 people who have done this.

While this is horrible and probably illegal (as the girls who have sex with them do not know they do this), it gets worse. They have evolved to throwing up this signal in all their group photos, including photos with the children wrestlers who look up to them. Our parents and the children’s parents do not know what this sign means and it doesn’t seem like anyone has gotten suspicious whatsoever.

As someone who strongly disagrees with this, I can’t stand the thought of she masting. I love my brother but this is absolutely disgusting. Is this just average teenage behavior or does this cross a line? And if so, what should I do about it? I hate being looked at as the snitch older brother, but this is horrendous. Help me Reddit, is this normal behavior for high schoolers?