Parsha Mitzvot: Acharei Mot: Mitzvah 197- 200 – Concept 149-151 & 159
The nakedness of your father’s sister you shall not uncover; she is your father’s flesh. The nakedness of your mother’s sister you shall not uncover; for she is your mother’s flesh The nakedness of your father’s brother you shall not uncover; do not approach his wife, she is your aunt (Vayikra 18:12-14).”
A man may not have relations with his father’s sister [same father and/or mother].
A man may not have relations with his mother’s sister.
A man may not have homosexual relations with his father’s brother.
A man may not have relations with his father’s brother’s wife (Rambam, Hilchot Issurei Bi’ah – The Laws of Forbidden Relationships).
The inclusion of the prohibition against homosexual relations with his father’s brother, when all homosexual relations are forbidden, is an indication that this is more than a prohibition against sexual relations; it is related to how one relates to a parent. Some Rishonim explain that any of these relationships is asserting one’s self over a parent’s immediate contemporary, a sibling, and indirectly, over the parent. Rabbeinu Ephraim believes that the switch in generations will create an unbalanced relationship.
My father zt”l insisted that nieces and nephews must always refer to an uncle and aunt by their title, Uncle… or Aunt…, even if they are of the same age, or younger. My father was an uncle when he was born and his nieces and nephews who were older than he all spoke to him as Uncle Yaakov even when he was little. It was considered honoring their parents.