Women Who are Forbidden for Marriage, Dought & clear, - * Is my father a mahram to the wife of my half-brother through my mother?

<-:=:-> I have a half-brother through my mother who has got married,
praise be to Allah. Is my father a mahram to his wife or not?
-
Praise be to Allah.
He is not a mahram to her, because he (the questioner's half-brother)
is not his son; rather she is the wife of his wife's son. So your
half-brother through your mother is the son of your father's wife, who
is your mother. Therefore the wife of your half-brother through your
mother is a "stranger" (non-mahram) to him, and he is not a mahram to
her. If your brother divorced her, it would be permissible for your
father to marry her, because she is not the wife of his son, and she
is not the daughter of his wife, such that she would be his
stepdaughter. So he is not a mahram to her; rather she is the wife of
his wife's son, therefore she is a non-mahram to him.
And Allah knows best.
Fataawa Samaahat ash-Shaykh 'Abdullah ibn Humayd (may Allah have mercy
on him), p. 221