This article is from the WSSF 2014 AFRMA Rat & Mouse Tales news-magazine.
By Karen Robbins
One thing I found to keep one litter of young male mice together as long as possible without fighting, was to not give them houses. Instead I gave them lots of hay and shredded napkins (they also got toilet paper tubes). This way there were no houses for one male to claim and defend as his own.