[human AU] Your assumption would be correct! He got around 6 years for statutory rape, and it's only because Yelena found out about it. Everything else he did, he managed to keep hidden. Boris was 16 at the time, and she insisted whatever they had going on was consensual, there was no recurring sexual relationship (she has her own reasons for defending Matthias), didn't want to press charges but Yelena sort of forced Boris to. I'm aware statutory rape usually has "lighter" sentences but because Matthias was involved in Boris' life since she was 6 (so he knew Boris' age when they had intercourse) and it was determined that Matthias was a caregiver/father figure in her life, he got more years than the average