Rabbits are highly social animals and normally prefer to be with another rabbit. They can suffer from boredom and develop behavioural problems when they live alone.
A good combination is a neutered male and a neutered female, or neutered littermates of the same sex. Rabbits that are brought up together will usually get on with each other, but if introduced for the first time as adults they may fight.
Aggression often is decreased by neutering of both sexes as aggression is commonly caused by hormones produced in the reproductive tract; however aggression can be caused by fear, learning or pain and neutering will not treat these.
As rabbits are prey species, they are not good at showing outward signs of pain so may be suffering significantly before anything is noticed. A change in the way a rabbit normally behaves can be an early sign he/she is ill or in pain. If a rabbit is not eating or is more quiet than usual, he/she is highly likely to be ill or in pain.
Rabbits should be handled regularly, particularly when they are young, so that they are not scared of being handled when they are adults.