Will mouse brothers fight?

Question
Ok, so a couple weeks ago my dad found a dead mouse in our shed. Attached to the mouse was a baby, still suckling its dead mother. We felt heartfelt sorrow for the little guy so we took him in. Later in the day we found another male... we have been keeping them in the same cage with one wheel, some nice seeds, and a lovely home. They made their nest together and have been getting along rather well, but I've been looking around a bit online and it says that male mice will fight, even if they're brothers. I don't wanna separate my babies, but if I have to, I will. Please tell me if they'll fight! I wanna know before it's too late!!!

Answer
Dear Nick,

Most males are too territorial to live together.  There are exceptions, exactly in the case of some litter mates.  Don't worry, you won't wake up one day and find one dead.  There will be a lot of chasing and squeaking.  This can be true of females as well-- they are just establishing dominance.  However, you should have contingency plans- i.e, plans for a second cage- for if/when it goes too far.  Too far in my book is if anybody is bleeding.  It won't be sudden, and you will have the chance to separate them in time as long as you are observing the cage frequently.  

Have fun with your two new pets.  

squeaks n giggles,

Natasha