The Forebears of the Husband are Mahrams for His Wife

Question :

Is husband's maternal grandfather considered to be the a Marham for the wife?

Answer:

All of the husband's forebears from his father's side and his mother's side are Mahrams for his wife, according to the Words of Allah, Most Glorified:
"the wives of your sons who (spring) from your own loins."

And the Hala'il (mentioned in the Verse) are the wives; and the male offspring of the daughters are known as sons of their grandfather from the mother's side, as is proven by the authentic Hadith of the Prophet in which he said to Al- Hasan bin 'Ali, may Allah be pleased with him:
"Verily, this son of mine is a Sayyid (i.e. a leader or chief)."

And he was referring to his daughter, Fatimah's son may peace and blessings be upon him and may Allah be pleased with her and her two sons, Al-Hasan and Al-Husain.

And Allah, the All-Powerful, Most High has made clear that 'Isa, the son of Mary is the descendant of Nuh and Ibrahim, peace be upon them, in His Words:
"And We bestowed upon him (i.e. Ibrahim) Ishaq and Ya qub, each of them We guided and before him, We guided Nuh, and among his progeny Dawud, Sulaiman..." up to His Words:
"And Zakariyya and Yahya and 'Isa and Ilyas, each of them was of the righteous."

And it is well known that 'Isa did not have a father, rather he was the son of a woman, and he is from the descendants of Adam and from the descendants of Nuh and Ibrahim, peace be upon him. As for the Words of Him, Most Glorified:
"who (spring) from your own loins."

And what is meant by this is the exclusion of the adopted sons, whom the people of Jahiliyyah used to refer to as their sons; and Allah forbade this in His Words:
"Call them (adopted sons) by (the names of) their fathers, that is more just with Allah.