Degu massive fights

Hello, my name is Jeffrey. I'm having some issues with my degus, I have 3, 2 boys (brothers) and 1 girl. I had the 2 boys at the beginning and after 3 months i decided to get a girl for breeding. i slowly introduced the girl to them. The first time they meet the two boys tried to mate with her at the same time, I took her away and put the girl in a different cage and the two boys in their cage. 30 minutes later the boys were mating with each other..... after 2 days of this they started fighting each other (roll together in a ball fighting), i separated the two boys but I was to late one had a injure by his eye (he's fine now), I only had two cages so i dressed the injury and put the girl degu with the injured boy and the other boy in the other cage to be alone, 2 months later i tried to reintroducing the boys together it was fine for 10 minutes but they started the serious fighting again, i intervene as soon as it started so no one was injured this time. should i just let them fight it out? I need guidance.

No, they will fight now and could do serious damage to one another because of the presence of the female. You should probably get at third cage to be able to house everyone separately, just to be safe.