The relationships of of Rex.
- Main article: Ahsoka Tano
- “Ahsoka Tano. I fought by her side from the battle of Christophis to the siege of Mandalore. And a friend of hers is a friend of mine.”
- ―Captain Rex, regarding Ahsoka[src]
Ahsoka and Rex met around the same time as she met Anakin, and she at first tried to pull rank on him during the Battle of Christophsis. He quickly put the fourteen-year-old in her place and she soon developed a respect for him, as the captain became somewhat of another mentor to Ahsoka. The two often saved each other's lives during the Clone Wars and shared a friendly bond similar to the bond Ahsoka shared with Anakin, but not as close. When meeting the Ghost crew, Rex told them that any friend of Ahsoka's was a friend of his, showing that they still had a close friendship sixteen years after her departure from the Jedi Order and renouncing her command position in the Grand Army.
Ahsoka and Rex renewed their friendship after he joined the Rebellion, and often enjoyed friendly teasing. However, Rex also expressed concern for his friend, particularly when Ahsoka left to go to Malachor.
Rex was deeply saddened when he learned of Ahsoka's apparent death.
- Main article: Cody
- Main article: Obi-Wan Kenobi
During the Clone Wars Rex and Obi-Wan worked with each other on some of their missions together. During a mission to capture General Grievous, Obi-Wan agreed with Cody that Rex is a smart man and believes that he always thinks on his feet.
Rex apparently never saw Obi-Wan again after Order 66, as he believed Bail Organa's words that Obi-Wan had perished.
- Main article: Kanan Jarrus
Kanan has a strong mistrust for Rex due to the occurrences of Order 66, while Rex feels that Kanan is not as competent a warrior as other Jedi he has served with. As they both started teaching Ezra, they conflicted on what Ezra needed to learn as a Rebel and bickered to the point of trying to show the other up occasionally.
When they went undercover as stormtroopers to rescue Ezra, Commander Sato, and his crew, they managed to work together well in a way reminescent of the Clone Troopers and their Jedi Generals during the Clone Wars, and when Rex chose to remain behind to give the others cover and time to escape, Kanan went back to rescue the old soldier, and finally put his animosity towards clones behind him when he gave Rex a salute of respect, which the captain gladly returned.
- Main article: Ezra Bridger
- “You were brave today kid. You jumped right in there to help. A great Jedi once told me that the best leaders lead by example. You do that well.”
- ―Rex's opinion as Ezra.[src]
Rex seems to serve as a grandfather figure to Ezra. Ezra finds Rex very interesting because of his past as a soldier and being in the Clone Wars. While Kanan refuses to trust Rex, Ezra believes they can. Ezra seems to be the bridge between Rex and Kanan because of Kanan's mistrust to clones. He was also willing to teach Ezra on how to man the AT-TE's turret. Ezra was the most saddened when the Rebels were forced to leave the clones behind and was the happiest to save them. Rex seems to see potential in Ezra as a leader.
Rex may see a little of Anakin and Ahsoka in Ezra.
- Main article: Saw Gerrera
- Main article: Kalani
Although they didn't meet until many years later, Rex and Kalani technically conflicted during the Clone Wars on the planet Onderon, until the Onderon resistance (which Rex had been assisting) to the Separatist rule proved to be more trouble than the planet was worth, and Kalani ordered a full retreat of Separtist forces from the planet, effectively driving them away.
Years later, while investigating an old Separatist base on Agamar, Rex, Ezra, Kanan, and Zeb were captured by a still-active group of battle-droids led by Kalani. Due to both Kalani and rex's animosity towards each other, as the clone and droid represented the two sides that had previously conflicted in the Clone Wars, both were eager to defeat the other. Only after the arrival of Imperial forcs and Ezra's words did Rex and Kalani bury their stigma towards each other and agree to join forces in order to escape the planet and the imperials.
After a close call, Rex and Kalani made epace with each other, their grudge settled, and parted ways on good terms.
- Main article: Darth Vader
- “The general I fought with was among the greatest of the Jedi. I trusted him with... my life more times than I can count. And I tried my best to keep that trust.”
- ―Captain Rex, regarding Anakin.[src]
During the Clone Wars, Rex and Anakin led the 501st and fought together side by side against the Separatists. Rex was very respectful to his general and obeyed his orders usually without question. However, it is unknown if Rex was aware that his General had turned into a Sith Lord, as Rex was with Ahsoka on Mandalore when the 501st marched on the Jedi Temple during Order 66.
- Main article: Agent Kallus
Kallus regarded the Clone Troopers to be obsolete and not a real threat whereas Rex bravely goaded Kallus after refusing to stand down or give up the rebels he was aiding. Kallus chose to make an example of Rex and his men, only to underestimate them and be sent running with his tail between his legs.