When I was a kid we got two males from the petstore and sure enough 30 days later I was baffled as to why one morning when I got up for school I had a hamster in there with them.
My mom was less than thrilled but once she explained that there was a baby gp in there I was happy as could be.
If you pick them up and hold them upside down (on their backs) and press gently just above their genital region a penis should pop out... however if you press too hard regardless if male or female itwill appear to pop out anyways.
So gentle is the key.
Courage is being scared to death and saddling up anyways. ~John Wayne