I was always told that my mother's father passed away when she was a toddler. Turns out that my grandma divorced him because he was having an affair with another woman. Guy had a son with the other woman, and my mom has a half brother she has never met.

This is the real "dark" one. My cousin Daniel is only a half brother to his younger sister but neither of them know it. My uncle was previously married to a woman but she left after she was bribed a huge sum of money by her FIL to leave the family (not sure of the reason why, though I assume it was because of an affair). She left behind my cousin and my uncle remarried another woman and had his younger sister. Apparently I'm the only one of my generation in the family who knows about it because my other uncle told me everything when he was drunk.