Sek is the eldest son of Tuvok and T'Pel, whose recorded message from Vulcan in Repression carries the hidden signal that turns his father against Voyager's former Maquis.
Sek is the eldest of Tuvok's four children. He is spoken of several times during Voyager's journey, including the news that he has made Tuvok a grandfather, and appears on screen in the seventh-season episode Repression.
There he is seen in a letter sent through the monthly data stream from the Alpha Quadrant, telling his father about family matters at home. Neither he nor Tuvok knows that a subliminal transmission has been embedded in the recording by Teero Anaydis, a fanatical Bajoran who once experimented with mind control for the Maquis.
The signal awakens conditioning planted in Tuvok years earlier, and he begins attacking former Maquis crew members and readying them for a mutiny. Sek's innocent message is eventually identified as the trigger.