Help understanding my bf

So my bf slept with a 14 yr old girl when he was 28 he said he was drunk. She was his roommates sister so he had made a friendship with her. He claims she looked older and acted older. My problem is I feel that she was a child and not of age to be having sex. I think the worst part was after he went to jail for a few years as soon as he got out he went back to her eventually they broke up because she cheated yet he still talks to her to this day. I'm just not sure how to handle this.

Update*** I found out his mom was 14 when she had him and she said she felt like an adult.

He did do 6 years of counseling he said he knows it was wrong but he doesn't see her as a child.

I'm still not ok with it.....