Clarification of the Forbidden Relatives by Marriage

Question:
My father’s wife is forbidden to me, there is no doubt about that. But is her mother forbidden to me?

Answer:
Only your father’s wife is forbidden to you. As for her mother, she is forbidden to you. Your father’s wife, your grandfather’s wife, your son’s wife, and your daughter’s son’s wife are forbidden to you, and there are other forbidden relatives besides these. As for the mother of your wife or the mother of your father’s wife, she is forbidden to your father. The mother of your father’s wife is forbidden to your father, not to you. And the mother of your mother’s wife is forbidden to your father, because He made the mothers of his wives among the forbidden relatives.