Is the son of the maternal uncle, who was suckled by the girl's grandmother (her mother's mother), considered her maternal uncle? And is it permissible for them to marry?

If a woman breastfeeds a child under the age of two, the child becomes her son through fosterage, and all those who are forbidden to her biological son are also forbidden to him. If a man is breastfed by a girl's grandmother, he becomes her maternal uncle through fosterage. Scholars have differed on the number of sucklings that establish prohibition. The Hanafis, Malikis, and Hanbalis (in one narration) held that prohibition is established by a single suckling. The Shafi'is and Hanbalis (according to the most authoritative view in the madhhab) stipulated five sucklings for prohibition, and this is the view given for fatwa. If there are five sucklings, then prohibition is established, and their marriage is not valid. If there are fewer than five sucklings, there is a difference of opinion regarding prohibition, and it is more prudent to adopt the view that considers prohibition to be established by any amount of suckling.