Spock infiltrated his family under this alias by claiming to be a cousin of Sarek, visiting his home while journeying to the family shrine to honor their gods. Sarek invited him to stay with them to break up his journey. While visiting, "Selek"'s young cousin Spock, prematurely began his kahs-wan across Vulcan's Forge. Selek followed Spock and subsequently saved him from death when he and his pet sehlat, I-Chaya, were attacked in the foothills of the L-langon Mountains by a wild le-matya. (TAS: "Yesteryear")
Despite being half-Human, Spock appears to claim his alias is fully Vulcan, as both parents have Vulcan-sounding names. This suggests that his Human side does not manifest itself in his outward physical features.
It was not explained if "Selek", "T'Pel" and "Sasak" were real relatives of Spock and his father. The idea of attempting to influence the course of one's life by visiting one's past self was later echoed by a similar scenario in TNG: "Firstborn" where Alexander Rozhenko traveled back in time to visit himself, posing as a family friend known as K'mtar.