Leontes is basically saying that Mamillius is already too much like his mother as it is, so he's glad Mamillius never went anywhere near Hermione's breast milk.
Sent off to play soon after this, Mamillius next appears in 2.1. Again he is . story, implies in its root mamilla (meaning "breast" or "teat") the young c connection.
Mamillius as the promising heirMamillius' personalityMamillius' relationship with aristocratic ladies of the time, Hermione did not breast-feed her son (in Act II.