I bought a new hamster for my old pet hamster since the other one died. these were syberian hamsters too. (I forgot the gender though, I believe they were both male). I put them in a cage, and the first thing they did was fought. But somehow after putting them in the cage a few more times, they got along just fine. I think holding them both one on each hand works also. I forget how I did it. It was a long time ago. All I know is it is possible. But also, One thing is for sure, two syberian hamsters will surely get into occasional fights even when bought at the same time. I've never had two hamsters that didn't fight. I suggest being careful though. When you put two stranger hamsters together, they come right at eachother for a fight. And I don't know how long they'd fight. Right now I don't have any hamsters. They kept dying for whatever reason. Either I didn't feed one right, or one escaped and got killed by my cat, or I didn't clean the cage enough. I was quite young, and probably not responsible enough to take care of a hamster.