Welcome Timmo, glad you came to join us, ask as many questions as you wish.
Are you sure both are male, or was it just the pet shop that said that?
Hopefully they are both male and one is just a podge, but we hear many stories of pet shops sexing dwarf hamsters incorrectly.
Anyway, I suggest you post your question under the either the russian campbell or russian winter white variety and someone with lots of dwarf experience will help!