Can you mate a robovski hamster with a syrian hamster?

I have a male syrian hamster and my sister has a female [dwarf] robovski hamster. We have been letting them stay together in a pin together to play. We have been monitoring their behavior and they don't seem to mind each other. We haven't left them alone though. My mom is a bit weary of the whole thing and thinks that they will mate. I truthfully don't think this is possible but could someone help me?