This is Rosebud, she will be two in january. She has been spayed, so it is totally safe to have her with all of these boys.-

And this is Romeo, who is two and a half-

And here is Louis, one of my two little babies, brothers I adopted from the humane society in July at 6 weeks old-

And his brother, Mendel-

And the whole mischief. Left to right, Rosebud, Mendel, Louis, and Romeo-

Oh, and I know Romeo looks very bald in the last picture. He is a very, very old pet shop rex rat. At a year old his coat started to thin somewhat and by the time he was two there were almost no guard hairs left. He now has a very thin, fluffy, soft coat that is incredibly tough to photograph. He has a few extremely thin areas and does look a bit bald even in person- I assure you, he is totally healthy. No parasites, nothing, just old. The vet noticed it last time we were there and asked about it, but when I said he was rex and told them his age, they weren't worried at all.
Also want to say- these are really BIG rats. Mendel and Louis haven't grown at nearly the expected rate and I'm supplementing them with extra protien to help with that, the rats in my area get HUGE. Romeo is 1.5 pounds, Rosebud is a pound, and my old boy Snitch (RIP buddy) was a whopping 2 pounder (not unhealthy either, just BIG)! It's expected for them to look a bit funny. There's no explanation as to why they get so big here, and it's not just me- I got Rosebud as an adult and she was a big girl. She came as a rescue.
(I've had comments on both Romeo's balding and the size of them before. Just clarifying.)