MOST HAMSTERS ARE SOLITARY TO A FAULT.
Hamsters value their personal space, to the point that they will sometimes fight other hamsters to the death if they invade their territory. Syrian hamsters are especially guilty of this, but there are some exceptions. Robo hamsters can be kept in pairs with other Robo hamsters, but it's best if they're related—otherwise, it can be very hard to introduce them to each other. There are a few other breeds that can be kept together as well, with varying degrees of success.
