[Amethyst_ice]

Hello

Im no good at sexing dwarfs but it would suggest they are female.

However, you mention one is much smaller than the other and I'd be concerned that keeping them together is the reason for this. Often one will dominate the cage and food bowl and this may be why one is smaller than the other.

If you really are set on keeping them together they will need two of everything and a large cage but it would be better to separate them. They really don't need to be together. The pet store should have explianed this to you, sadly.