Meerkats are matriarchal, and the alpha female gets to choose the alpha male. In addition to the alpha couple, the gang consists of beta males and beta females who are subservient to the alpha meerkats and leave the gang by the time they're three years old.
Beta males voluntarily leave the community to become the new dominant males in another gang, or to form a new gang with unrelated females.
Beta females, however, are forced to leave. They're evicted from their gang by the alpha female during her pregnancy. Any or all beta females may be evicted, but pregnant beta females are the most likely to go. Not all beta females return to the gang after eviction. Some return after the alpha female has given birth to her pups, but others join outside groups permanently.