The Sunni schools observe: The maternal grandfather is included in the category of distant kindred who do not inherit in the presence of a sharer or residuary. Accordingly, the maternal grandfather does not inherit with the paternal grandfather, the brothers and sisters, the children of full or agnate brothers, the paternal uncles or their sons. When all of them are absent and there is no sharer present, according to the Hanafi and the Hanbali schools, the maternal grandfather is entitled to inherit. According to the Shafi’i and the Maliki schools, he is never entitled to any inheritance.
The Imamiyyah say: The maternal grandfather inherits with the paternal grandfather and with brothers and sisters of all kinds, and, likewise, he excludes paternal and maternal uncles and aunts of all kinds from inheritance, because he belongs to the second category of heirs, whereas they belong to the third. Hence if a maternal grandfather is present with a full paternal uncle, he takes the whole estate to the exclusion of the paternal uncle.