The victim is a little boy. Obviously I don't have a problem with homosexuality between consenting adults but it just makes it all the more unexpected. The mother, looking back, had plenty of control over the contact with her daughter (the victim's twin) but had fewer reservations about contact with the boy.
Fortunately, I went away for college and don't have to be there day to day, but I am going to be babysitting the twins soon. I know I'll have to be right in the middle of the situation.
Thank you so much for the support and response.