The mother of the maternal grandfather, and the mother of the paternal grandmother’s father: do these grandmothers belong to different lines?

Yes. The first belongs to the maternal line, and the second to the paternal line. Thus, we elevate each one through the chain until she reaches an inheriting relative, and then she inherits. But how does she inherit?

We say, as mentioned earlier: if the grandmothers are equal in degree, they share one-sixth between them; but if they are not equal, it belongs to the closer one. However, the established school of jurisprudence holds that grandmothers—whether through the mother or through the father—belong to a single line. One wonders how the mother of the maternal grandfather can belong to the paternal line!

They say: because each of them is called a grandmother. This matter is one of juristic reasoning, for neither the Quran nor the sunnah provides a detailed explanation of the inheritance of distant kindred. For this reason, the scholars have differed greatly concerning it.