I was trying to compile a list of all the sentient species (or in some cases, subspecies or supra-ethnic groups which consider themselves distinct) in Star Trek which are direct biological relatives. I thought it could be fun to discuss how Star Trek treats interstellar speciation, which the novels have gone into much further length from canon.
Vulcans
Romulans
Remans
Watraii (Vulcan's Soul)
Kenisians (TOS - Crisis of Consciousness)
possible cousin: Zami (ENT - Rise of the Federation: Tower of Babel)
possible cousin: Mintakans (TNG - "Who Watches the Watchers?")
possible ancestor: vulcanoid Arretians (TOS - "Return to Tomorrow")
possible descendant: Chenar (DTI - Watching the Clock)
Andorians and Aenar
Caitians and Kzinti/Ferasans
Edosians and Triexians (TAS - "Beyond the Farthest Star" et al. and New Frontier)
Lurians (DS9: "Emissary" et al.) and Baladonians (TNG - "The Next Phase" and TTN - Absent Enemies)
Rilnar and Zahl (VOY - "Year of Hell, Part 1" and VOY - A Pocket Full of Lies)
Humans
Neyel (TLE - The Sundered and TTN - The Red King)
Possible descendant: Zcham (DTI - Watching the Clock)
Vulcans
Romulans
Remans
Watraii (Vulcan's Soul)
Kenisians (TOS - Crisis of Consciousness)
possible cousin: Zami (ENT - Rise of the Federation: Tower of Babel)
possible cousin: Mintakans (TNG - "Who Watches the Watchers?")
possible ancestor: vulcanoid Arretians (TOS - "Return to Tomorrow")
possible descendant: Chenar (DTI - Watching the Clock)
Andorians and Aenar
Caitians and Kzinti/Ferasans
Edosians and Triexians (TAS - "Beyond the Farthest Star" et al. and New Frontier)
Lurians (DS9: "Emissary" et al.) and Baladonians (TNG - "The Next Phase" and TTN - Absent Enemies)
Rilnar and Zahl (VOY - "Year of Hell, Part 1" and VOY - A Pocket Full of Lies)
Humans
Neyel (TLE - The Sundered and TTN - The Red King)
Possible descendant: Zcham (DTI - Watching the Clock)
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