I wouldn't recommend adding any other dwarfies to your group, pairs that haven't been raised up together since they were very young, have little to no chance of ever living together peacefully. Like amity said, pairs are unnatural and it's better for hamsters to live on their own, but if you're set on not separating them, then you'll need to constantly be monitoring them and their behavior. Unfortunately though, a majority of pairs end up falling out
If you want to get more hams, simply buy a 40 gallon tank for each hamster you wish to get! Though they're very cute, their well being must be put before convenience, and all decisions must be made in their best interests. Good luck and best wishes
