While pet rabbits can survive alone without another bunny living with them, they can get very lonely and sad, as rabbits are naturally herd animals. No matter how much human attention they receive, that does not replace attention from a fellow rabbit friend.
When one rabbit is introduced to another rabbit, they may not always get along. However, they will always be very curious when they first meet, and can become close friends after bonding for a while. Keeping close supervision on bunnies when they first meet, however, is very crucial, as they could get into a fight and hurt each other.