Grandmother Too

I read on here about a mother who discovered that her son and his grandmother were obviously having a relationship. I have been a having a sexual relationship with my grandson for the last four years. His mother – my daughter – knows all about this and has no problems with our doing this. She said if we were both comfortable and happy with it, that it was fine with her and why not?
All I can say is that we are both quite happy and pleased with this arrangement, and that I strongly suspect that I am not he only lucky grandmother out there.