In nature, mice live in colonies usually consisting of one male and several females. They enjoying living together in groups, and females should never be kept alone.
The best number of mice for a cage is two, although you can keep as many as five together without too much risk of fights breaking out. Females are best kept together. Male mice are territorial and tend to fight after the age of 2 months, so don’t house male mice together. Don’t put an unaltered male and female together unless you are prepared for litter after litter of baby mice.
Be sure to spend individual time with each of your mice if you want them all to be tame. Some will be shy and will need more coaxing. Be patient with these more timid mice so you will be able to easily handle all your small pets.