Star Trek: 10 Alien Species That Are Actually Related

Six different sentient species evolved on the Xindi homeworld: the Primates, Arboreals, Reptilians, Insectoids, Aquatics, and the Avians. Every species shared similar forehead ridges, but they each occupied a different niche in the Xindi ecosystem.

The different species frequently got into conflicts with each other. The battles escalated into a civil war that wiped out the Xindi-Avians and destroyed their homeworld. To maintain peace, the five remaining species established the Xindi Council, a governing body run by two representatives from each species. After this point, the Xindi became much more united, though arguments and conflict were still commonplace.

In the 22nd century, the Xindi were tricked into attacking Earth by the Sphere Builders, a faction in the Temporal Cold War who convinced the Xindi that humanity was destined to destroy them. We don't know much about what happened to the Xindi after this conflict, but they likely joined the Federation afterwards, since Daniels mentioned that there was a Xindi Starfleet officer serving aboard the Enterprise-J in the episode Azati Prime.