Hiya,
With my Robos i sometimes let the females have two litters back to back, which means that i have take the first litter away from the mom usually as early as 21 days old - the babies are absolutely fine in same sex groups after that, although it can take me a few weeks to accurately sex them!
I usually keep my Robo babies until they are 7 or 8 weeks old, just to be 100% on the sexes, but once i am completely sure of the sexes then i believe they are safe to go to their new homes as long as they are over 6 weeks and are going in pairs or small groups.
This is just my personal procedure to follow, and i am sure other people do things differently, but sometimes there are only two of each sex in a litter (or less!) so i suppose that from 21 days old they would be safe to go to new homes if the sexing was accurate and they were already in a pair, but, personally i would never let any of my babies go before 7 weeks old. I like to feed them up and give them plenty of handling and plenty of toys to play with and also to sex them accurately before they go to their new homes
Just my personal oppinion though
I am sure your two hammies will be fine, especially if it was a small litter and they were the only two of that sex - they will be completely happy and used to being the way they are.
Good Luck with them,
When i had my litter of Syrians i removed the male babies at 3.5 weeks old as this was already an accidental litter and i didnt want any more 'accidentals'
but the males stayed together for the longest amount of time without fighting, but the females had to be split into separate cages at around 6.5 - 7 weeks old. Most of the babies went to their new homes when they were between 7.5 and 9 weeks old.
Kind Regards,
Tammy x