That is fine - my response was informed by knowledge of therapeutic approaches and knowledge of world history, so it was well thought through. The idea of the support forum is to help support the OP. A lot of people voiced that she'd be better off without this man. This reaction is understandable, but it trivializes the OP's predicament - surely she could on her own come up with "Since I have only been with the bf for 9 months, it is easier to reject him and move on than to persevere and look for a solution." So "just move on" is something OP must have considered already, and decided not to choose. That brought her to the forum - looking for ideas. So I think we should give her ideas rather than just spill out personal bias. Plus, since the mother did not raise the child at all - the OP was very clear on that and even put GSA in the title - I do not see why people react so strongly to the situation. She is not the woman who changed his diapers, took him to kindergarten and quietly wiped her tears, fed him, chaperoned him on school trips, kissed his boo-boos when he would scrap his knees, implored him to keep his room tidy, dealt with carpools etc. She simply gave birth to him, but did not raise him. And they are not producing genetically compromised babies. So the many reactions of the people on this thread - such as yours - are based on calling his biological parent a Mother - that triggers the reaction. She is not his Mother - she is his biological parent. He has a Mother - his adoptive parent. Does he have sex with his adoptive Mother (who was the one changing diapers and chaperoning trips)? No, he does not. So he is not crossing any societal boundaries, loosely understood as ethical boundaries, because the societal boundary involves Mothers/Fathers, not biological parents. The distinction is critical.

I am not sure, but I would not be surprised if some of the reaction comes from a taboo associated with men having sex with women who are much older. There is no taboo on the reverse situation, gender-wise - women have sex with men older than their parents a lot, but for men, it is unusual. So a bias against "younger man, older woman" maybe a subconscious undercurrent among the many responses on this thread. So let me ask you this question: are you CERTAIN that you have absolutely no hangups about r/s across age groups in which the man is younger, and that you would not have any objections to this man's having sex with a woman in her 60s to whom he had no genetic ties? Are you absolutely, 150% sure that you are reacting specifically to the biological ties and not to the fact that an older woman is pleasuring a much younger man? If the answer is "yes, I am certain", the next question is - would you be able to identify a very strongly held bias if the bias were on a visceral level, ie. you never gave the bias any deliberate thought? Because, you know, some people simply cringe at the mere thought of a 60+ year old woman having ANY kind of sex.

What would you say to those two questions?

***

Going back far in history, we ultimately owe the English alphabet to the Ancient Egyptians, and in the upper classes of Ancient Egypt incest was common, so there is at least some case for looking at this issue with sober, neutral, calm eyes and not just reacting out of a vague "this is an ultimate taboo" place.