Kestra Troi

Kestra Troi is the first child of Lwaxana Troi and Ian Andrew Troi, born in 2329. Being half Human, half Betazoid, it was unclear whether she would develop full telepathic abilities or only empathic ones. She died shortly after the birth of her younger sister, Deanna Troi, in 2336. She died from drowning.

After her death, her mother had a bizarre reaction to her grief, and attempted to wipe the girl's existence from her memory. Her father Ian accepted this for a time, but planned to confront her. He died before he could. Lwaxana would fire her valet, Mr. Xelo, for keeping some evidence of Kestra's life. (TLE novel The Art of the Impossible)

The truth about Kestra would not become known to Deanna until 2370, when a telepathic encounter with the Cairn unlocked the supressed memories within Lwaxana's mind. ("Dark Page")