Many years ago when I was 23, I got married to a widow. this widow had a grown up daughter. My father fell in love with her, and soon they got married. This made my Dad my son-in-law and changed my very life. See below how:
My daughter was my mother too because she was my father's wife!
After a few years I became father of a baby boy complicating the matter further. My son became the brother-in-law of my father!