My boyfriend was adopted as a baby and reunited with his biological mother 10 years ago (he is now in his 40s).

Quite early on in our relatationship he admitted to having sexual feelings for his biological mother and told me that he would masturbate over her and fantasize about having sex with her. It was the first time he had ever told anyone about it.

I was a little taken aback but I know that it is not unusual for adopted sons to feel sexual attraction to their mothers and at the time I found it pretty harmless. They were just fantasies. Or so I thought.

Recently he has confessed to me that he is actually been having a full blown sexual relationship with her for 10 years! I was too shocked to say much. He also said that he used to have intercourse with her but that he hasn't lately but she sucks and wanks him off all the time when they are together (at least one weekend a month, sometimes two). I have told him that I don't want him to have intercourse with her anymore because that is just too much. Handjobs I can sort of live with. He agreed to that.

He says it is like she is a ***** who will pleasure him anytime he wants and that the orgasms she gives him are out of this world because they are so wrong. I also get the impression that he is using her sexually as punishment for abandoning him and he admits to being rough with her in a way he would never treat me.

I am trying my best to not be judgemental and to understand that this is a psychological disorder and not being crazy or perverted. And to appreciate the trust he has placed in me by confessing this to me and while I have no feelings of jealousy towards the mother the fact that they are having a sexual relationship bothers me terribly as it is just so so wrong and I worry very much about the implications...

I don't know what to do. I wish he had never told me as I don't know what to do with this knowledge. I want to help him stop this as it cannot be anything but extremely emotionally damaging but how?? He is not in love with her, it is clearly only a sexual attraction and not a romantic one. Apart from this he is a well adjusted person who has a succesfull career, many friends, very close to his adopted family who are all lovely people.

My knowledge of psychology is limited and there is no way he would confide in a therapist, I am the only person in the world who knows. And tbh I don't get the impression he really wants to stop having sex with her because the sensation and attraction is so intense. He did stop for a while in the beginning of our relationship but it has since then started again. He also says that his biggest desire is for me to watch her suck him off and that most of the time when she is pleasuring him he is looking at photos of me. And while I guess I could watch it I feel it is wrong of me to encourage this unhealthy relationship.

Please help me, I don't know what to do? I am trying to not judge or be harsh and to accept and be understanding but still subtly let it show that it worries me and I have said that I do not think it is healthy. How can I help without making him see a therapist? Is there any hope that he will one day stop this, that it will just fizzle out?