Is it permissible for a Muslim man to marry his paternal uncle's daughter whose mother breastfed his (the man's) mother, given that the number of feedings is not remembered?

The suckling that prohibits marriage and necessitates prohibition is five full sucklings, according to the preponderant opinion. If you doubt the number of sucklings (five or fewer), then the prohibition is not established. However, it is better to be scrupulous and not marry the daughters of the wet nurse, to avoid the disagreement of those who hold that prohibition is established by a single suckling.