I think my step son really wants to tell me about his abuse

Edit: I wasn't trying to hurt his feelings. Just hearing in detail about child s.a is heavy

My step son is 17. He was having some complicated feelings because his cousin just graduated from grad school and this is a cousin who sexually abused him when he was 4 and the cousin was 16. Most of my husband's side of the family went to his graduation. They aren't very involved with our family. We talked about his feelings and I asked did he remember it and he said yes. It's the earliest memory he has. He asked if I wanted to know exactly what happened and I said no because that's really heavy. He seemed like he wanted to tell me though and that he was disappointed that I said no. He's been to therapy over this when he was small.