Sherlock Holmes fakes his death in 1891. In the period that follows, he secretly has a relationship that leads to the birth of a son, Ryland, who becomes a soldier in the British army during WWI.
Ryland adopts the Holmes surname by the time his son Alwine is born in 1914. Alwine is a Member of Parliament, in recognition of his grandfather's considerable reputation, and his own inherited faculties, and he is among those who support Winston Churchill during the years of WWII.
Laiken Holmes is born in 1938. She works for MI6 during the Cold War, meeting the American spy Tom Grayson, whom she marries in 1956.
Newland Grayson is born in 1958. He enters the world of computers, which are fast blossoming in his formative years.
Wolcott Grayson is born in 1980. He follows the family business of his grandparents, navigating the aftermath of the Eugenics Wars as an agent of the CIA.
Marwood Grayson is born in 2007. In his adult years, WWIII has begun, but he works the home soil as an ordinary detective, following a much older family tradition.
Ewald Grayson is born in 2032, and initiates a family tradition that continues for the next two generations (Byford, born in 2054; Edric, born in 2078) by serving as a United States senator. He's the second of the Graysons whose life is defined by WWIII.
Sherwin Grayson is born in 2103. His grandfather Byford was a boy when First Contact occurs, but for him life with Vulcans and the interstellar community is routine. Like his great-great-grandfather Marwood, Sherwin is interested in the fantasy legacy, and opts for a return to the informal, private detective occupation shared with their distant ancestor Sherlock.
Bromley Grayson is born in 2135. He works as an ambassador to Vulcan.
Amanda Grayson is born in 2168. She becomes a school teacher, but can never escape the shadow of her father, whose activities frequently bring Sarek of Vulcan to their family home. Amanda and Sarek fall in love.
Spock is born in 2230. Amanda is keenly aware that her son is the child of two worlds, and that his Vulcan side will often dominate him, but she frequently reminds him of his human heritage as well. The many generations of her family sometimes seem trivial to the young Spock, but he grows to appreciate the printed adventures of Sherlock Holmes, as written by his friend and colleague John Watson. He finds Sherlock's analytical mind to be surprisingly logical (although at times, quite human), and this is one of the ways he is, in the privacy of his own thoughts, able to reconcile his heritage.
Although, many years into his Starfleet career, when he references his ancestor, obliquely, he is quite justified in believing few will make the connection, or appreciate it, as he does.
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In Star Trek VI: The Undiscovered Country, Spock quotes the Holmes axiom, "When you have eliminated the impossible, whatever remains, however improbable, must be the truth." The Holmes connection is likely inspired by director Nicholas Meyer, who earlier in his career had also directed The Seven-Per-Cent Solution, which is of course a Sherlock Holmes movie. Meyer first directed a Star Trek film with The Wrath of Khan, in which Spock meets a premature end, mostly to accommodate Leonard Nimoy's wish to cease performing the role. Then Nimoy, and Spock, return anyway. Meyer has for years insisted the death should have been final, which is ironic, given that Holmes' creator, Sir Arthur Conan Doyle, had arranged a similarly premature death, only to bring him back, too. The irony concludes with Star Trek Into Darkness, which evokes Wrath of Khan, including a death scene, which fans have been discontent about for years, even though it pivots the scene around themes relevant to the story around it, just as the original had, with no particular need to suggest finality.