Esteban is the son of Cecil and Carlos. He was adopted by the couple two years before "A Spy in the Desert", but his parents agreed that they needed to keep some of their personal life off the air, and so Esteban's existence was never mentioned. He has started speaking in short sentences six months prior to A Spy in the Desert and has a passion for exploring and discovering the world around him. He is named after his uncle, Steve Carlsberg. He takes after both of his fathers and loves strawberries and giraffes.
Outside of A Spy in the Desert, Esteban's existence wasn't explicitly mentioned until the episode, "C****s", where Cecil recalls what the clouds looked like the day he and Carlos had their son. Before that, his existence had only been hinted at. In the episode, "The General", Carlos tries to convince a Cecil living in an alternate timeline that they are in love and married by sending him pictures of their family. Later, Cecil receives a voice message from Carlos talking about his and Cecil's family that is unlike the one he has in that timeline. Carlos paused when he was about to say what else they have, then asked if this message was going to play on-air, then dismissed what he was about to say. Carlos was likely about to mention Esteban in that scene, but because of their shared agreement to never mention him during a broadcast, he didn't. In response, Cecil stated he called him back, saying he loves Carlos and their dog, then paused before listing what else he loves, then finished by saying he loves their life together. Cecil was likely about to mention their son, then stopped himself, having regained his proper memories and also remembering their agreement.
In "Bravo", Cecil mentions that it is difficult for him and Carlos to go out to see live theater due to a number of obstacles, including the need to hire a babysitter to do so.