Is it permissible for me to marry my maternal uncle's daughter, knowing that my mother breastfed my maternal uncle (her brother)?

Suckling establishes prohibition (of marriage) just like lineage. So, whoever is suckled by a woman becomes a son to her and to her husband, the owner of the milk. This applies exclusively to the suckled child, not to his siblings. Therefore, the suckling of the questioner's mother of his maternal uncle does not prevent the questioner from marrying his maternal aunt's daughter, unless there was suckling between them or another cause for their being unmarriageable (to each other), knowing that the suckling which prohibits (marriage) must consist of five full sucklings during the first two years of life.