Captain James Tiberius Kirk, played first and foremost by William Shatner, is a man who needs no introduction. In-universe, he's one of the most decorated Starfleet captains in history, and in real life, he remains one of the definitive faces of the entire "Star Trek" franchise. You may not even know, for example, that Kirk has a son named Doctor David Marcus, played by Merritt Butrick. David first appeared in the film "Star Trek II: The Wrath of Khan," working alongside his mother, Doctor Carol Marcus, on Project Genesis aboard the Regula I research station. This left a lasting impression on Kirk, negatively coloring his impression of Klingons, but outside of a brief reference in the fourth film, David never appears again.