Male mice rarely get along at all. When very y oung and not fully sexually mature, they can get along but once fully sexually mature, it is best not to house them together. They will fight, even kill eachother in competition. However, they may learn to live together, if they are brothers but I think this is more rare.
The last time I had males together, it was in a large cage with plenty of hiding places, two food dishes and two water bottles, at opposite ends of the cage. This seemed to work for a few weeks until I separated them and paired them off with females.
ANother group of mice I had I made a mistake on the sex of one of the 'females' and couldn't understand why the male was attacking one of his females all the time. When I double checked and realized I didn't have 3 females with one male, but two males and two females, I separated the picked upon male. If I didn't it wouldn't have survived much longer.
So, your best bet would be to bring the two mice back and get two females.
-----
PHLdyPayne