I saw on tv incest betwen mother and son

This can happen in a dysfunctional family. An example would be having a drunk father that always come home and beat the mother. The son gets angry with the father and tries to comfort the mother. The mother being a in a very vulnerable state can make wrong decisions as to finding someone to protect her, which she just so happens the only other men she knows is her son. It starts as a simple innocent hug, and the cross the line with a kiss and blah blah blah. You get the picture.