Can I Introduce A New Hamster With An Old One...even If They Are Related?

I have a black bear hamster. She is only a week or two old and i got her from a pet store where she was with all her siblings together. I only got one. I have had her for a couple of days and she looks sad and i think its because she misses her siblings. So i was wondering if i could get a brand new cage and go back to the same store and get one of her sisters. I would then put both of them into the same NEW cage at the same time. Is this ok?