My wife and I have been married for about four years now. This man is my real father. We live together as parent and child after my mother passed away. And the woman here is her mother, which makes her my step-mother or 'mother-in-law'. Sometimes she would stay over at our place when visiting her daughter, and we lived peacefully until... one day, I found out that my dad was having such intimate relationship with his own daughter-in-law's mother... I couldn't say anything; I just stood there speechless.