Is the one whom my grandmother breastfed along with my maternal uncle considered my maternal uncle (khal)? Knowing that my grandmother also breastfed my mother and her female cousin’s elder son.

Whoever suckled from your grandmother becomes your maternal uncle through suckling, and thus is a mahram to you, for Allah Almighty says: "Prohibited to you are your mothers and your daughters and your sisters and your paternal aunts and your maternal aunts and your brother's daughters and your sister's daughters and your mothers who have suckled you and your sisters through suckling..." (Quran 4:23). And for the saying of the Prophet, peace and blessings be upon him: "Suckling prohibits what lineage prohibits." Therefore, the son of your maternal uncle's paternal aunt who suckled from your grandmother is considered a mahram to you because he is in the position of your maternal uncle.