Not to excuse him because obvs I have no more information on exactly what occurred than anyone else, my partner as a 13-16 year old used to tell older guys he was above the age of consent if he fancied them. He could grow a full beard so while (imo) they should have done their due diligence and paid attention to his maturity, they were not deliberately committing an offence. He was contacted a couple of years ago by a wife who had found historic messages between her husband and him when he was under age - my partner told her he honestly couldn't remember how old he claimed to be but she she reported it to the police as child molestation (there was apparently a lot of cheating, of which this was part so she was being vengeful). My partner had to make several statements to the police about it in the end and was very annoyed by the inconvenience.
Obviously if the victim has reported it ( having realised they were a victim) the above is irrelevant, and given the age gap with him and his husband and the fact he's gone without a fight, I'm definitely more than 50/50 there was something untoward involved.
Sadly age gap relationships where there is a power imbalance are quite common even between men.