Is it permissible to marry a male cousin (son of a paternal aunt) if the mother breastfed him only once or twice, knowing that she also breastfed another brother of his several times?

Scholars have differed regarding the number of sucklings that establish prohibtion (of marriage). Some have held that a single suckling establishes prohibition, while the Shafi'is and Hanbalis have stipulated five sucklings. This latter view is the one we (usually) issue fatwas upon. Accordingly, if your paternal aunt's son did not suckle five times from your mother, it is permissible for him to marry you, as the prohibition due to suckling is specific to the suckled child only, not his siblings. However, we advise against marrying your paternal aunt's son who suckled from your mother, even if only once, as a precautionary measure and out of consideration for the view of those who consider prohibition to be established by any amount of suckling.