In Start Trek: Discovery Michael Burnham is Spock's foster sister (having been fostered by Spock's parents).

Discovery is set 10 years before TOS, and fits within the same universe. That being the case, in TOS, or any other pre-Discovery work, does Spock mention, or even allude to, having a human foster sister?

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    I have read that Dorothy Fontana decided that Spock would be an only child on both sides of his family in order to increase the drama of his relationships with his parents. So any Star Trek writers who heard of and followed that decree would naturally avoid mentioning any siblings of Spock. Commented Dec 18, 2017 at 18:55
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    This is yet another instance of Discovery not caring whatsoever about continuity. It should not be surprising at this point. Commented Dec 20, 2017 at 8:44
  • @HamSandwich Spock having a sibling he never mentioned? Yup, nothing in existing continuity to support that. Commented Mar 23, 2020 at 12:46

2 Answers 2



However, that's not necessarily such an unusual thing. Spock was tight-lipped about his family, also not mentioning Sybok, his half brother, until the fifth movie, or who his parents were until the second season of TOS in "Journey to Babel". In both incidents, the dialogue makes it clear that his fellow crewmates, including his captain, were unaware of who his family were.

Dialogue from Star Trek V: The Final Frontier:

SPOCK: You do not understand me, Captain. Sybok, also, is a son of Sarek.
KIRK: He's your brother brother? You made that up.
SPOCK: I did not.
KIRK: You did too. Sybok couldn't possibly be your brother because I happen to know for a fact that you don't have a brother.
SPOCK: Technically, you are correct. I do not have a brother.
KIRK: You see?
SPOCK: I have a half-brother.
KIRK: I've got to sit down.
McCOY: Let me get this straight. You and Sybok have the same father but different mothers.
SPOCK: Exactly. That is correct. Sybok's mother was a Vulcan princess. After her death, Sybok and I were raised as brothers.
KIRK: Why didn't you tell us this before?
SPOCK: I was not prepared to discuss matters of a personal nature. For that I am sorry.

And from "Journey to Babel":

SAREK: Doctor. My aides and she who is my wife.
(He holds out his right hand with two fingers extended, and a human woman steps forward to touch them.)
AMANDA: Captain Kirk.
KIRK: Our pleasure, madam. As soon as you're settled I'll arrange a tour of the ship. Mister Spock will conduct you.
SAREK: I'd prefer another guide, Captain.
KIRK: As you wish, Ambassador. Mister Spock, we'll leave orbit in two hours. Would you care to beam down and visit your parents?
SPOCK: Captain, Ambassador Sarek and his wife are my parents.

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    There's also the technical issue: Burnham was a foster-sister and not a blood relative at all, so Spock, when asked about his family, could be very literal about it. Commented Dec 18, 2017 at 16:14
  • Great answer, thank you.
    – Moogle
    Commented Dec 19, 2017 at 11:06
  • At least Sybok made sense given it is quite reasonable that Sarek would have had a first wife he was bonded to. Commented Feb 13, 2020 at 2:38

First of all, Spock never mentioned a sister, but neither did his parents. Even Sarek on his death bed never mentioned having a daughter.

Also if Spock had a sister, who played an important role in Starfleet, Capt. Kirk would have known about her.

Now if the writers had made her a cousin to Spock, that I could have believed. After all, Amanda was human, and could have had brothers and sisters; one of which could have died.

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    I've removed the unnecessary rant about the writers. Other than that, this is a bit thin as an answer; even if it's hard to prove a negative, please consider backing up your post with quotes and the like, like the previous answer did.
    – Jenayah
    Commented Mar 10, 2020 at 5:04
  • I think it was made quite clear at the end of season 2 that every record about the spore drive and the Discovery are to be eradicated and any knowledge about the ship or its crew being strictly confidential. So no, neither Sarek nor Spock would give anything about it away and Kirk may not even know about the ship, even less about who raised Burnham. Commented Mar 11, 2020 at 9:05

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