The first child of William Riker and Deanna Troi, born aboard the USS Titan, who died of a rare disease after the synth ban closed off the one treatment that could have cured him.
Thaddeus Troi-Riker, known as Thad, is described in the first-season Picard episode Nepenthe and is seen only in family pictures. Born on the Titan, he grew up on starships and longed for a homeworld of his own.
He filled the gap by inventing one, a world he called Ardani, complete with its own cultures and a string of constructed languages. His younger sister Kestra still uses one of them, Viveen, the tongue of the wild girls of the woods.
Thad contracted mendaxic neurosclerosis, a silicon-based illness that could have been treated using a culture grown in an active positronic matrix. After the attack on Mars such research was outlawed. His parents left the Titan and settled on Nepenthe for the healing qualities of its soil, but he died there before the events of the series.