Is this sexual abuse?

My friend and I are mutual with a boy named alex my friend *caleb" was always convinced to spend 1 on 1 time with Alex because Alex would claim no one hung out with him. EVERY TIME when Caleb went to Alex's house Alex would grope his thighs and chest and lay in his lap while my friend would beg him to stop. My friend Caleb even explained he was molested and did not like this attention and Alex replied "oh, your fine/it's fine". One time Alex's grandmother walked in and told him to stop and Alex refused and said fuck off grandma. This wasn't unusual either for example Alex guilt tripped me into watching porn with him at a sleep over once. The problem is Alex and Caleb are cousins and Alex is a year younger than Caleb. Is this sexual abused and if so what should I do.

P.S. I'm not sure if I can go to police either because I had pinched Alex's chest (alex is trans) 3 times in the 2 and a half years we've known each other and he's telling people I groped him after me and Caleb called him out for "making us uncomfortable" and now we are thinking this could be much more.