Conjoined Twins

I keep an eye on stuff like this, because I have a fictional species that naturally runs to bicephaly.

Cool!

Did I mention I started a Traipah story once wherein these twins are born with a kind of telepathic Gift such that they are one mind in two bodies? And to a lesser degree, there's a pair of Duenicallo in my third Traipah novel (one I'm working on now) who can sense each other's presence, receive and send some sensory data, and suffer greatly when they're too far apart for very long. They are still unique individuals, which makes their bond a lot different from the one-mind-two-bodies pair, though.

Oh, and also on Traipah, there is a long tradition of "Ancestor carrying." Very wise, intelligent, or otherwise important people are chosen to have their zirr'kah embedded into a willing host. In other words, their mind is telepathically copied to the mind of another, and stored there. These copies ride in the background and can be referred to, or they can be allowed to Front. It's usually done at the end of the donor's life, so they can continue to enrich society after they die. Only the most worthy minds are chosen for this. It's entirely voluntary, but it's a great honor. And when the host is about to die, the Ancestors in hir mind are transferred to another host.

Post-first contact, many human anthropologists studying the Ah'Koi Bahnis believe that some of the god-forms, like Shao'Kehn and Ahndahn, were originally Ancestors, people who were once alive on Traipah, whose true identities have been lost with time. The Ah'Koi Bahnis themselves tend to reject this notion, partially for obvious reasons, and partially because they see it as an insult to their record-keeping abilities AND to the process of Ancestor transfer; there is almost never degradation of the memories of the consciousnesses transferred, even after thousands of transfers; also, the Ah'Koi Bahnis excel at record-keeping and preservation of records. There are Ancestors who can be traced back to before The Reformation (though those are rare), and they can still remember their original lives with just as much clarity as they did in life.

Naturally, it is also a great honor to be chosen as a host for an Ancestor consciousness. And it's not uncommon for hosts to have up to between 6 and 12 other minds in their brain. Though the more Ancestors one takes on, the shorter one's own life gets (though most hosts do live to be at least 120).