Ruling on giving zakah to grandmothers
Question

I have wealth on which I pay zakah to my needy relatives, namely my grandmother who is my mother’s mother, and my grandmother who is my grandfather’s wife but she is not the mother of my father. They have children other than me, but I heard a hadith from the Messenger of Allah (peace and blessings of Allah be upon him), the meaning of which is, “Give it (zakah) to your relatives.” How sound is this hadith? What is the ruling on previous years when I have paid this zakah, noting that I have not kept track of the number of years when I did this?
Praise be to Allah.The hadith mentioned is saheeh; the Prophet (peace and blessings of Allah be upon him) said to Abu Talhah al-Ansaari, when he wanted to give in charity a date-palm grove of his called Bayraha’, “I think that you should give it to your relatives.” (Saheeh, agreed upon). That was concerning voluntary charity. But in the case of zakah, there are more rulings to be borne in mind: if the relatives are not in the direct line of ascent or descent, it is permissible to give zakah to them if they are poor, and this will be an act of charity as well as upholding ties of kinship. This also applies to your grandfather’s wife, if she is not your real grandmother and she is poor and has no children to spend on her. You have to make up for what you have spent on your maternal grandmother (your mother’s mother) and on your (paternal) grandfather’s wife, if she was of independent means because of someone other than yourself spending on her.
And Allah knows best.