Parsha Mitzvot: Acharei Mot: Mitzvah 191 – Concept 140
The nakedness of your father’s wife you shall not uncover; it is your father’s shame (Vayikra 18:8).” A man may not have relations with his father’s wife (Rambam, Hilchot Issurei Bi’ah – The Laws of Forbidden Relationships).
“It is your father’s shame,” meaning you are treating your father’s relationships as purely physical, and that he did not intend for you to exist. (Based on Rokeach)
I once overheard a father repeat to my father zt”l what his son had said: “The only reason I exist is because you wanted to sleep with my mother!”
My father responded, “That is exactly what the Torah means when it says, ‘it is your father’s shame.’ He is attempting to shame his father, but in truth, he is declaring his own shame. This is another reason why we must teach the laws of relationships with such care; if our children view relations in a casual way, they will think less of themselves!”