Everyone's favorite Klingon Worf had a son in Star Trek: The Next Generation — and the character has been played by five different actors throughout the franchise (so far). Worf's son Alexander Rozhenko was a surprise: after a brief relationship in the TNG season 2 episode "The Emissary," half-human, half-Klingon K'Ehleyr became pregnant with Worf's child but never told him. Two seasons later, in the episode aptly named "Reunion," Worf and K'Ehleyr's paths crossed again, and she introduced him to his son, Alexander. Although Alexander never became a regular character, his presence was felt throughout Worf's narrative journey, and his return in Star Trek: Deep Space Nine marked a turning point in Worf's character arc.
In a tragic twist of events, K'Ehleyr perished in "Reunion," and Worf found himself responsible for a son he had only just met. Alexander had not been raised as a traditional Klingon, and although Worf himself was adopted by humans at a young age, Worf and Alexander struggled to find common ground because of K'Ehleyr's vastly different principles.
Alexander appeared in 12 episodes of Star Trek: eight episodes of TNG, followed by four appearances in DS9. Several of these episodes focused on Worf's relationship with Alexander, such as "Cost of Living," in which Worf and Alexander go to Troi to resolve ongoing conflicts, and the delightful "Fistful of Datas" episode that sees Worf and Alexander trapped together in a Western-themed holodeck program. The following is every actor who has played Alexander in Star Trek.
Jon Steuer
Alexander was introduced in the TNG episode "Reunion." By this time, Worf son was already a toddler. Because Alexander mother, K'Ehleyr, was killed by the treacherous Klingon Duras (K'Ehleyr was investigating Duras to uncover his role in a conspiracy that had harmed Worf's social standing considerably), Worf claimed Alexander as his kin — despite having previously stated he did not wish to share his dishonor with his son. In this episode only, Alexander is played by the late Jon Steuer, who left the acting industry in the mid '90s and pursued a career in music. When the character returned, he was played by an older actor — likely to accommodate labor laws that govern how long child actors of each age can work (which includes the hours they spend in a makeup chair).
Brian Bonsall
For most of the character's run, Alexander was played by Brian Bonsall. Bonsall first appeared in the role in the TNG season 5 episode "New Ground," and continued to play the role until his final appearance in the series: season 7, episode 21, "Firstborn." Bonsall is thus the version of Alexander most Trekkers think of for Worf's offspring.
Marc Worden
After TNG concluded in 1994, Worf transitioned into Deep Space Nine, joining the cast as a regular for season 4 in 1995. Alexander didn't move with him to the station — as Worf explained, they had continued difficulties getting along, and Worf felt it would be better for everyone if Alexander lived on Earth with his grandparents. However, in the season 6 episode "Sons and Daughters," Worf is surprised to encounter Alexander on the Klingon ship the Rotarran. Although he is only approximately 9 years old, Alexander has matured into a man (Klingon's mature faster than humans do) and is trying to reclaim a Klingon identity for himself.
Alexander is played by Marc Worden in DS9, since the character had matured into adulthood and therefore needed to be played by an adult. After "Sons and Daughters," Worden's Alexander appeared only once more, in "You Are Cordially Invited," the last canon appearance of the character in Star Trek.
James Sloyan
In the TNG episode "Firstborn," Worf and Alexander meet a mysterious Klingon named K'mtar (James Sloyan), an advisor to the House of Mogh. By the end of the episode, K'mtar reveals himself to actually be Alexander from forty years in the future; as an adult, Alexander witnessed his father being murdered, and he blamed himself because for what happened. Future Alexander then travelled back in time, vowing to turn his past self into a traditional Klingon warrior in order to prevent Worf's murder. Thus, Sloyan also played Alexander — but as an adult.
Richard Martinez
The last actor on this list only appeared as an image on Star Trek; Richard Martinez was used for a framed picture of Worf and his son Alexander seen in Deep Space Nine season 4, episode 1, "The Way of the Warrior" and season 6, episode 16, "Change of Heart." Martinez was uncredited for the short stint, and the next time Alexander appeared in the Star Trek franchise, he would be played by the adult actor, Marc Worden.