Incest is happening in India also as it is happening in other parts of the world. According to myth, sex between a teacher and student is also comes under incest. We can leave that chapter. In case of blood related persons like Father, Mother, Son and Daughter, there are many reported cases. Recently lot of cases were disclosed that Father abused his daughter sexually and daughter become pregnant etc. Nearly 10 years ago, one of my relative pointed out me a man who has a daughter in his sister. (Later this lady died in an accident, that was the circumstance, my relative's disclosure). I have no idea about incest between a mother and son.