Star Trek: Picard season 1 introduced Will Riker and Deanna Troi's children, Kestra and Thad, both of whom have names that are references to previous Star Trek canon. Star Trek: Picard premiered in January of 2020, and was set 20 years after the events of Star Trek: Nemesis, the final film that focused on the cast of Star Trek: The Next Generation. The series' main character is Patrick Stewart's iconic Jean-Luc Picard, and the first season featured several familiar faces from TNG, including Picard's former first officer Will Riker and his wife, ship's counselor Deanna Troi.
Picard was reunited with Riker and Troi in the episode "Nepenthe" when he and the android Soji Asha sought refuge with them after Picard saved Soji from a Romulan attack. "Nepenthe" was the first appearance of Riker and Troi since Star Trek: Nemesis, and revealed that in the intervening years, the couple had had two children, a son named Thad and a daughter named Kestra. Riker and Troi had subsequently retired from their roles in Starfleet and moved to the planet Nepenthe when Thad fell ill with a degenerative neurological disease that ultimately took his life. This meant that, although Thad was an important presence in the episode, he was only seen in photographs throughout it. After Thad's death, Riker and Troi continued to live on Nepenthe with Kestra.
In what was clearly a nod to discerning fans, the creative team on Star Trek: Picard chose to give Kestra and Thad names that reference previous bits of established Star Trek history. Both kids have family names, Thad's name coming from Riker's side of the family and Kestra's coming from Troi's. Thad is named after his ancestor, Thaddius Riker, who was a colonel in the American Civil War. Colonel Riker was introduced and briefly discussed in the Star Trek: Voyager episode "Death Wish," where it was revealed that a member of the Q Continuum had saved the colonel's life during the war, an act which later had made it possible for him to have descendants, including his namesake. Although the spelling of the name was changed slightly to "Thaddeus," Thad's name is still clearly meant to be an homage to Riker's ancestor.
Kestra's name is a reference to an episode of Star Trek: The Next Generation, and holds a slightly darker place in Star Trek history. TNG season 7 featured the episode "Dark Page," in which Deanna Troi's mother, Lwaxana, fell into a coma unexpectedly while onboard the Enterprise. With the help of a telepathic species called the Cairn, Troi entered her mother's mind and learned that Lwaxana's coma was caused by the memory of her first child, Kestra, who died by drowning at a young age. Lwaxana had never fully processed the trauma of Kestra's death, but Troi was able to help her start by the end of the episode. Troi was only a baby when her older sister died and thus had no memory of the incident.
The story of Kestra Troi-Riker's namesake is sad on its own but lends an even more heartbreaking twist to Thad's story. Thad's death means that both Deanna and Lwaxana Troi lost their first child at a relatively young age. This was likely an intentional parallel on the part of the creative team and is a subtle Easter egg for fans who remember Star Trek: TNG. Star Trek: Picard season 1 had many Easter eggs to the wider Star Trek universe, but Riker and Troi's children's names were arguably one of the more interesting ones for fans to pick up on.