OP should talk to his parents about getting a lawyer.

Here is my line of thinking;

OP is clearly in a broken home. The mom knows about this relationship and hasn't done anything. She instead put the onus on a 15 year old child to report the crime to the police, not her.

OP is a victim. I have a feeling OP is being groomed by this 35 year old. While I understand the letter of the law in regards to child porn, can you show me any case law where an obvious victim who was being groomed was successfully charged?

The dad thinks that a 35 year old with a 15 year old is okay.

My line if thought was that a teacher or counselor WOULD call CPS. OP needs to get the fuck out of this toxic household.

Full disclosure: I don't work with children nor am I a criminal defense lawyer. I only made this post to let you inside my line of thinking. If it is wrong, I will delete my comment.