Help! We got two Russian dwarf hamsters last November. We got them young from a large and reputable UK chain pet store; we understand they are brothers. Photo below! Pinky's white and very small; Brain is grey-brown, and has grown to twice the size of Pinky, though you can't tell in the photo! They live together in a hamster cage, and one keeps picking on the other. Edit: Having looked, and read up a bit, I wonder if they're not boys but girls! I know hammies are hard to sex.. well, I can't see any kind of male appendages!! Think they may both be girls. Anyway - still need advice! Brain usually seems happy enough. He exercises way more than the little one; he's always on his wheel, and he doesn't seem to over-eat. Very easy to handle, a real sweetie, not an agressive bone in his body. Pinky is okay to handle but a lot more nippy. He nests and burrows a lot more; doesn't exercise so much, but doesn't put on any weight at all - really tiny. But every day I hear squeaking - Pinky gets on top of Brain (who just falls over and lies on his back) and just biffs him about! Despite being twice Pinky's size, Brain doesn't put up a fight at all, just squeaks and waits for it to stop! He doesn't seem overly traumatised by it, but I worry. Why does one pick on the other, when they seem mostly to get on okay? There's no biting or injuries, but I'm worried that he never stands up for himself (and it's weird that the tiny one is the boss!). Is this okay/normal? I don't want to interfere unless I need to but I want to be sure my hammies are okay... it would be so sad to have to separate them as I know they don't like to live alone.