Solkar was the first Vulcan ambassador to Earth and, as such, was the answer to a crossword puzzle which a female crewmember was trying to solve while forced to live in Enterprise NX-01's catwalk for several days. Captain Archer supplied her with the answer. (ENT: "The Catwalk")
Sarek followed in Solkar's footsteps and became an ambassador. Sarek wanted his son Spock to do the same, but Spock chose a career in Starfleet instead. (TOS: "Journey to Babel") He would eventually become an ambassador himself, after Starfleet.
Background information Edit
According to the Star Trek Customizable Card Game and Stellar Cartography: The Starfleet Reference Library ("Stellar Cartography", p. 25), Solkar was the Vulcan captain of the T'Plana-Hath who greets Zefram Cochrane in Star Trek: First Contact.
In an unpublished interview with Larry Nemecek, "The Catwalk" writer Mike Sussman stated that he believes this as well, citing the wording in Archer's dialogue in "Horizon", in which he refers to Cochrane's first contact and says, loosely, "I don't remember anyone going after the Vulcan ambassador with pitchforks and torches when they first landed."