Star-Lord and Gamora initially bonded after they fought each other for the Power Stone. As members of the Guardians of the Galaxy, Star-Lord and Gamora's romantic relationship had just started to develop in the MCU.
A quick, comedic scene in Vol. 3's Orgocorp heist teases some potential romance between Peter Quill and Nebula, but James Gunn claims that it was never going to become anything more (per The New York Times).
Before Gamora, Quill dated many women, which included a Rajak woman, then a Kree girl and an A'askavariian. However, all his previous girlfriends had either attempted to kill him or have departed with him on friendly terms. He once had an affair with a Garmosian Duchess before it was struck off his criminal record.
Recently, a battle with the Olympians unlocked Peter's latent powers, turning him into the Master of the Sun. He was also stranded in an extra-dimensional world called Morinus, where he became romantically entangled with two local nomads named Mors and Aradia, and where he fathered a son he called Rocket.
After all, their relationship was built over the course of the past two Guardians of the Galaxy films. By the time they were officially together in Infinity War, Gamora was killed off shortly after, so the audience didn't really have time to enjoy Quill and Gamora as a couple.
The assassin Gamora becomes perhaps the most complex of Star-Lord's relationships amongst the Guardians. Quill holds her in high esteem and the frustrations between the two eventually relent as they began a romantic relationship.
It turns out that Nebula star Karen Gillan very much believes that Nebula does have a little crush on Peter Quill, and during a recent interview with The New York Times, director James Gunn expanded on that a bit and believes that there could be something there.
In Avengers: Infinity War, Star-Lord and Gamora kiss following a flashback of when the mad titan Thanos (Josh Brolin) adopted Gamora as a little girl. Before they kiss, Gamora makes Star-Lord promise to kill her if necessary so that Thanos cannot learn the location of the Soul Stone.
So much so that Tony was arguably the best father figure that Nebula has ever gotten in the MCU. Thanos had an abusive relationship with his adopted daughters. While he favored Gamora (Zoe Saldana), he was harsh and downright dismissive of Nebula.
Sometime before the Red Skull overthrew the United States of America, Star-Lord stepped up to be the Emperor of the Spartax Empire, while marrying L'ssa who bore him two children, Meredith and Jason.
Another particular thing about Quill and Gamora is that they didn't break up, she died. And then he was turned to dust and was brought back, but didn't feel the passing of time, so technically he was still grieving for his lost love when he saw the Gamora variant that was brought to his time.
Star-Lord's sister, Empress Victoria, is determined to destroy the Guardians of the Galaxy, setting the stage for a sibling clash of cosmic proportions.
Mantis tells Star-Lord that she is his sister near the end of the Disney+ special as part of the explanation for why she wanted to kidnap Kevin Bacon for him. The confirmation of Star-Lord and Mantis' relationship allows Guardians of the Galaxy Vol. 3 to begin with it known to the characters.
We've seen Baby Groot, and how much Gamora loves him in Volume 2, and how much he loves her. Like... that is his mom. And so there's a particular sadness here, where she doesn't remember him. "That, to me, is one of the saddest things in the entire movie, that your mother doesn't know who you are.
The movie's post-credits scene revealed his adolescent form, which is the term James Gunn prefers over designating Groot as a teen. An adolescent is defined as being between 10-19 years old, but Gunn's preference could mean he is a pre-teen.
At the end of the movie, Star-Lord resigns from his position as captain/leader of the Guardians of the Galaxy to finally return to earth (where he was only once—for Tony Stark's funeral—since he was abducted as a child right after his mom died) to spend more time with his grandfather.
