Oh, and just to introduce them, I have five boys - only one of them has a name unfortunately (I'm not good at naming rats - the vet has them down as Rat 1 etc based on the order in which I needed to take them in to see him!)
I have two older boys (around two years old), Skippy and his brother, and three younger ones (coming up to 11 months). None of the young ones are named, so I tend to refer to them by description - the belly (he has a big white patch on his belly), the ear (he has a notch in his ear, maybe from a fight before he came to me?) and the tail (all three of them have dark fur and dark tails, but the tip of his is pink.)