Sister's milk

My wife had a great deal of trouble having our son and she passed away 2 days after from complications of the birth. I'd a son and no wife and with family support I would recover. My wife has a sister 3 years younger and she had failed university and was looking for work. So, as my career was going great, I hired her as my son's nanny. She would care for her nephew, and I could return to fulltime work. As breast milk is best for newborns, my sister-in-law suggested getting hormones treatment to get her started producing milk for her nephew. As she wanted too, I agreed and that was it she of course only needed hormones to start, once started nature took over. After several month watching my sister-in-law breast feed my son, my attraction to her increased. Needless to say, we ended up as lovers and my son is now 4 and has a stepsister/cousin 2 and a stepbrother/cousin in his aunt's belly for another 2 months. But to him his aunt is mommy as he is too young yet to understand, but he has his mother's picture in his room, and he is told it of his mother.