In the beginning of the series, Abeke is Shane's friend. Shane was appointed with the task of training her. But eventually Abeke realized that she really belonged with the Greencloaks, and even felt bad about leaving Shane, because he was 'the only one that really appreciated her'. Frequently Abeke would remember her time with Shane and miss him, and by Blood Ties, they meet once again in a battle, where Shane (and Conor) go out of their way to block a Conqueror blow aimed at Abeke. When Conor asks who Shane was, Abeke gets flustered and evades the question. Up to Rise and Fall, Abeke still continues to believe that Shane is a good person. She cared for him very much, and the feeling was mutual. They go on Shane's family ship to Greenhaven, and once there, Abeke reveals that she was "honored that he'd started feeling safer with her". Then when Shane is revealed to be the true Devourer, Abeke blames herself harshly for letting herself fall into his trap. In the final battle, Abeke resists Shane's attempts to make her feel sorry for him, telling him that she is sorry, "because you mean nothing to me." In The Book of Shane: Vengeance, Shane admits that he has a weak spot for girl archers and that he cares for one, therefore revealing that he possibly cares about Abeke not just as a friend. In all of Shane's regrets about the things he has done, he regrets losing Abeke -- his only true friend -- the most. In The Burning Tide, Shane saves Abeke from Uraza by sacrificing his life for her to live, and him to die.
In Heart of the Land, Shane's death was revealed to still deeply affect Abeke, but she is able to move on and express her opinion of Shane to Conor. Later on, Worthy speculates to himself that Shane was in love with Abeke, but would not admit it. Worthy continues to hint at Shane's favoritism of Abeke in The Wildcat's Claw, saying that the Redcloaks were allowed to joke about the other members of the Four Heroes, but never Abeke.
Drina is Shane's sister. When she was infected with the bonding sickness, Shane frequently came to visit where she was bedridden. Though Drina would sometimes lash out and unintentionally hurt her brother, Shane loves her, as she is family. In a flashback, young Drina was even shown to cry out of worry when her brother was bitten by a snake. In Rise and Fall, when Drina is unexpectedly killed by mind-controlled Iskos, Shane still went along with his 'good guy' plan, but confessed to actually have been truly horrified by his sister's death.
Shane would often accuse his uncle Gar of stealing the title of 'The Devourer' from him. Shane doesn't like taking orders from his uncle, whom he believes to be cruel. In The Book of Shane: Vendetta, Shane encounters Renneg in a dream but the wolverine starts to talk in Gar's voice. Gar tells Shane that he always knew he hated him for being violent and cruel. Shane apologizes and tells him that he never meant to hurt him. But Gar answers that he hurt him anyway, and that was Shane's nature.
Shane has a mostly negative relationship with Zerif, shown in Book 1 of the Book of Shane: Vengeance, where Shane is rather suspicious of him. Zerif in return doesn't think very highly of Shane. Shane is furious when Zerif pledges his loyalty to Kovo in The Evertree, causing him to fight on the Four Fallen's side.
Anya was Shane's guide though the Amayan forest, where they travel to a temple and find a group of Conquerors. Anya was nervous when she found out that Shane was The Devourer, confessing that she'd imagined him to be "cackling like a madman". Later it was discovered that Yumaris paid Anya to lead Shane to her hiding place, which was just below the temple. Anya also wielded a bow and arrow to get closer to Shane, which he mocked her for later, saying he doubted whether she'd ever even picked up a bow, and that he had a 'soft spot for girl archers'. They get along decently during their track trough the forest, but Shane is outraged when he finds out she was paid to lead him to the temple. Regardless of his anger at her, Anya follows him underground (wanting to know what was going on between him and Yumaris). When there, Anya hears Shane's story and is sympathetic.
When Yumaris runs, Anya wills Shane to forget about the old woman and come back to the surface, telling him he can change and become a good person and let "someone else play the hero". Shane refuses and follows his old teacher, explaining to Anya that he didn't want to be good or evil.
Tahlia was somewhat close to Shane during the war. When she "died" in Fire and Ice, Shane decided to pursue a new plan, where Gerathon would control one of the Four Fallen (Meilin), perhaps out of grief for Tahlia and to get revenge. It's also possible that Shane borrowed the idea of the Redcloaks' white masks from Tahlia.
Rollan, like the other Four Fallen kids, is not very fond of Shane. Rollan is the one to accuse Shane of lying about his spirit animal, which he and Conor found dead in Nilo. In The Burning Tide, they are still tense around each other, but Shane is able to combat Rollan's sarcasm with his own, which seems to make Rollan respect him more. Shane even smiles when Rollan makes a joke about him wanting to get the Greencloaks 'out of his hair'. In The Wildcat's Claw, Worthy comments that Shane would let the Redcloaks joke about the Greencloaks, especially when it was about Rollan.
Conor openly despises Shane for most of the series, showing uncharacteristic anger whenever Shane would appear. It seems to mostly be due to his jealousy of Shane's friendship with Abeke. Shane seems indifferent to Conor and his contempt towards him. In Fire and Ice, he waves to Conor from afar as if they were old friends, to which Conor says he'd like to punch Shane in the face, and Rollan agrees. Despite Conor's earlier ill feelings towards Shane, he is the one to convince the rest of the Four Heroes that Shane should accompany them to The Evertree.