Is the person who suckled from his grandmother along with his maternal uncle considered a brother to all his maternal uncles and aunts, and therefore forbidden to marry their daughters?

All children of your foster mother are your brothers and sisters through fosterage. Your mother also became your sister through fosterage because you were suckled by your mother's mother (your grandmother). The sons and daughters of your maternal uncles and aunts are the children of your brothers and sisters through fosterage, and thus you become their maternal or paternal uncle through fosterage. Therefore, it is not permissible for you to marry their females.