Personally, I will not going to condemm or approve "Peter" and his Mum. It is a personal choice that they both made in a consensual manner. No one forced either into it. Yes, there are some moral issues here. I am sure there are some people out there who have had fantasies or fleeting sexual thoughts of their relations. But I would assume it is all part of growing up. It is up to the individuals to decide whether they want to enact it or ignore it. Aside to Henky-san, ignore the naysayers who choose to badmouth you. All you have done is to provide the individuals with a place to share their secrets. Of course, there may be a need to sometimes highlight that one's actions is not the most appropriate, but who are we to judge at the end of the day. Most important thing of all is the individuals can keep in mind that they should not satisfy their own needs or wants at the expenses of others. Cheers!