One Male and one female can be housed together as a breeding pair, but they will generate litter after litter. Male siblings can be housed together as long as they are together from birth and kept together after weaning. Same with females, we keep up to 5 siblings in a cage. You cannot mix multiple males and females in a cage, as the males will start to fight and the stress level rises. Once a male has been exposed to a female they will often fight with other males.

Thank you for your response, apologies I should clarify that my question is regarding housing the male and female mice in the same room but they would be strictly kept in separate cages.

I think housing different sex mice in the same behavioral room is OK. But remember to do habituation before the tests, for 1-2 hour, in order to let mice adapt to the environment, like light, temperature and humidity. Besides, clean and disinfect the equipment, like chamber, by 70% alcohol thoroughly when changing to different sex mouse.

Thanks to you both for answering my question!