The following story is from N. Wirth's (1976) Algorithms + data structures = programs.?

. I married a window (let’s call her W) who has grown-up daughter (call her D). my father (F), who visited us quite often, fell in love with my step-daughter and married her. Hence my father became my son-in-law and my step-daughter became my mother. Some months later my wife gave birth to a son (S1), who became the brother in-law of my father, as well as my uncle. The wife of my father , that is, my step-daughter, also had a son (S2). How can we represent this story in predicate calculus? And how can we prove that “I am my own grand father”?