Is it permissible to marry a paternal cousin who was breastfed by the the younger brother, and does the ruling differ if the one who breastfed was the mother or her mother?

If your cousin (daughter of your paternal uncle) was suckled by your mother, then she becomes your foster sister, and it is unlawful to marry her. However, if your brother was suckled with her by her mother or by another woman, and she was not suckled by your mother, then it is permissible for you to marry her due to the absence of a prohibitive fosterage between you two. Prohibitive fosterage consists of five or more sucklings.