In the novels, Cyrus is described as "sweaty" and Blair hates him strongly at first especially when he moves in with his son Aaron and his dog Mookie. But soon they are a part of her family.
Cyrus makes his first appearance in Bonfire of the Vanity when Eleanor introduces him to Blair. However, Blair is disappointed once she meets Cyrus because he is not who she had in mind. She schemes to get rid of him, by revealing to Eleanor that Cyrus cheated on his first wife like Harold did on her, but her plan ultimately backfires when he invites Cyndi Lauper to her birthday party. After making up with Eleanor, Cyrus moves into the penthouse. In The Magnificent Archibalds, Blair finds out Cyrus proposed to Eleanor and she feels she's being pushed out of her own family, especially after he eats her pie she made in honor of Harold. She skips dinner and eventually return home, to find Cyrus and Harold chatting like old friends and Blair decides she's willing to let Cyrus be a part of her family.
After Bart Bass' funeral in O Brother, Where Bart Thou?, Cyrus decides he doesn't want to live another day not being married to Eleanor. They plan an impromptu wedding for the next day in their apartment. Blair, Dorota, Serena, and Aaron attend the wedding. Cyrus throws a seder dinner in Seder Anything and invites his mother, who hates Eleanor, and Rufus, Lily, Serena, Allen Levy, and Gabriel Edwards also attend. After Blair is rejected from Yale, he offers to use a favor to get her an interview at NYU, which she eventually agrees to let him do.
In The Last Days of Disco Stick, Blair brings the Tisch students to a private performance from Lady GaGa, and explains Cyrus is an old friend of hers and she wrote Poker Face after they played poker together.
Cyrus and Eleanor move to Paris permanently in The Treasure of Serena Madre. They return to visit in The Unblairable Lightness of Being and find Dorota worried because her parents are coming and have no idea she is unmarried and pregnant. Chuck throws her a wedding, and Cyrus attends with ceremony with Eleanor. He buys Dorota and Vanya an apartment in Queens, which Eleanor disagrees with at first, but then decides it's a good idea. He and Eleanor are at the hospital when Dorota gives birth in Last Tango, Then Paris, and is named one of Anastasia's godparents, along with Eleanor.
After Blair and Louis get engaged, Cyrus and Eleanor return to throw them an engagement party. With a mutual interest in ornithology, Cyrus is able to win Sophie over and get her to approve of Blair too.
Cyrus hosts a Yom Kippur dinner in The Fasting and the Furious, and the same day he and Eleanor find out about Blair's pregnancy. At the dinner, Blair is presented with a contract about the custody of the baby and Cyrus, being a lawyer, quickly finds all the faults and tight guidelines contained in it. He attends Blair's wedding in G.G., and walks her down the aisle with Harold on her other side.
Cyrus makes his last appearance in New York, I Love You XOXO when he marries Chuck and Blair at the Bethesda Fountain. In the time jump, he's shown to still be married to Eleanor.
- Eleanor Waldorf (Wife)
- Eleanor Waldorf (Wife
- Eleanor Waldorf (Wife)
- Alice Rose (Ex Wife)
- Kim Li (Fling)
- He's an avid ornithologist.
- He is a veteran of the Vietnam War, where it is hinted he rescued a comrade under fire. It was in Vietnam where he had an affair, leading to the end of his first marriage.
- He used to play poker with Lady GaGa when she was a Tisch student. He is also friends with Cyndi Lauper.
- He wears sports socks.
- He slurps his soup.
- He is Jewish.
- His catchphrase is "not enough!"
- He can speak Polish and Yiddish.
- He considers himself to be a hugger.
- He's a lamaze coach and has been present while many of his clients give birth.