Like many Garde children, John was raised by his grandparents. Henri tells John that John's Grandfather loved to make people laugh and was always making jokes and pranks with his invisibility Legacy, and once even pranked Henri. Four's grandparents complemented each other greatly, his grandfather was carefree while his grandmother was more quiet, reserved, very intelligent, and made sure everything went to plan behind the scenes. John remembers that his Grandfather saw him off in the airship that was earthbound. Both his grandparents hugged him and made their goodbyes before returning to the battle. His Grandfather had Lumen, like John, and Invisibility Legacies.
His parent's names were Lara and Liren. Henri mentions that although they weren't allowed his father often came to see John. John has a vision of his father battling the Mogadorians during the invasion and dying. His father has the elemental manipulation Legacy, same as Six. Henri mentions that he met John's mother once and she was reserved and maybe even a little shy like his father.
|“||We always joked about it but you were my father, the best father I could have ever asked for. I'll never forget you, not for a minute for as long as I live. I love you, Henri. I always did||”|
–John, to Henri
Sarah is a human female with whom John has an intimate relationship starting after his stay in Paradise, Ohio. Sarah's friendly and caring nature and John's attraction combined to create their relationship which began friendly and eventually became romantic. Physically speaking John and Sarah progressed as far as kissing however emotionally they are described as in true love. Sarah tells John at the end of the novel that she will wait for him and does not come with him, Sam, and Six as they leave Paradise. She is suspected of turning him into the FBI after he implies having feelings for Six, but in the Rise of Nine, Sarah Hart was found in the same holding cell with Six in the Government base in New Mexico. Later when found by Number Four, she was rescued and she fought side by side with the other Garde. She then started traveling along with Number Four and the other Garde when they escape the government base together after fighting Setrákus Ra.
In the Fate of Ten, Sarah was mortally wounded while Marina was knocked out and died whilst on the phone with Four, saying her last words.
|“||Sam is my best friend.||”|
–John Smith, The Rise of Nine
Sam is initially polite to John and the two become friends after Sam warns him to stay away from Sarah due to her possessive ex-boyfriend. After witnessing John's Legacies during a fight on Halloween, Sam pulls a gun on John and reveals that Sam's father is believed to be abducted by aliens and that he believes John has come for him. Initially, Sam is lied to by John and their friendship continues until he needs Sam to help him save Henri. After this, Sam is told about John's true nature. He accepts John as a friend and alien and shows extreme loyalty in the battle against the beasts in the climax of the novel. Sam leaves Paradise with John. Apparently, Sam vowed to find his father no matter what even if it means fighting Mogs who abducted his father. After traveling with John and Six, they soon believed that Sam's father, Malcolm Goode, was a helper of the Garde on Earth. Sam becomes jealous of John because both of them are interested in Number Six. After Six left to find a Garde in Spain, Sam and John went to the Mogadorian base and found Nine. Sam Goode was then captured because John didn't have time to save him when he went running to look for his father. He was later reunited with his father and John and traveled to Nine's safehouse. John advises Sam about his crush on Six and encourages him to express his feelings. When Mogs attack Nine's safehouse, Sam's father is injured badly and is on the verge of death. John decides to save Malcolm instead of rescuing Ella who has been kidnapped since he doesn't want his best friend to go through what he went through with Henri. Sam thanks John for saving his father's life.
|“||She's the strongest person I've ever met||”|
–John to Nine, about Six
Back on Lorien, Six's and John's parents were best friends who joked that they'd end up together. John first meets Six as her first goal in uniting the Garde. Her interventions save his life during his first battle with the Mogs. During the course of The Power of Six, John becomes drawn to Six despite his feelings for Sarah and his friendship with Sam. They constantly flirt with one another and John comes to admit his feelings for her when she tells him she likes him despite the fact that he can be an idiot. When John is reunited with Sarah he admits that he loves Sarah more than Six. Things become awkward between them until Six forces John to patch things up with Sarah. They talk things out and Six says she understands that John loves Sarah more than her and she accepts that. They remain as good friends.
|“||His loyalty, his bravery very nearly make me weep. He's a hundred times smaller than the beast yet he stands tall, vowing to fight.||”|
–John Smith about Bernie Kosar
|“||He's reckless, arrogant, selfish and just flat-out rude.||”|
–John about Nine, The Rise of Nine
When John meets Nine in West Virginia, he is impressed by his Legacies and combat abilities to compare them to Six's but becomes concerned about the fact that Nine seemed to enjoy fighting too much. Still, they work well together and escape after which they make plans to recover at Nine's home in Chicago. Nine takes care of Four like he is a younger brother. Even though Nine is stronger than Four, he does not underestimate Four's intelligence. When John was unsure about the leadership role that was thrust upon him, Nine was able to give him his version of pep talk that lifted his spirits. John mentions that Nine's sense of humor is infectious. They did fight, and it ended in Nine dangling him off a roof, by which John was embarrassed. In United as One, before they attack the West Virginia Base, Nine goes to John and apologizes for all that he has done to him. In the case he did die, he didn't want it on his conscience. After he apologizes, he gives John a quick hug and tells him he is his brother and that they will make it out alive.
|“||Every school has one, a tough guy, a bully, whatever you want to call him.||”|
–John Smith, I Am Number Four
John and Mark hated each other at the beginning. Mark constantly bullied John because of his interest in his ex-girlfriend Sarah Hart. During the Halloween hayride, his friends attack John and kidnap Sarah. John manages to overpower all of them and throw them in the river, but not before making Mark apologize to Sarah, who in return slaps him. When John saves Mark's two dogs and Sarah from a house fire, Mark's attitude towards John changes. When he goes to John's house to thank him, he gets mixed up in the fight between Henri and John and goes to Paradise High School and gets caught in the middle of the battle with the Mogadorians. John makes Mark promise to keep Sarah safe during the battle and he keeps that promise even after John left Paradise. He helps John during the battle and even carries him to safety when he falls unconscious. He along with Sarah helps John to leave Paradise. In the later books, it is revealed that Mark is hosting the They Walk Among Us website and that he needs help. John sends Sarah to help. After the death of Sarah, John goes the loric ship to see her and Mark is there. John says a few words to her and Mark berates him for how selfish he is for taking Sarah and including her in all of this. On the way, John gets stopped by Mark who punches him in the abdomen and then nicks his chin with an uppercut. John then asks him to take Sarah's body to her parents. Mark agrees, but only after dissing John. John soon sees Mark again in front of their hidden military base, but he is not himself. He has black veins, pale skin, and resembles a Mog-human hybrid. John is taken prisoner by Phiri Dun-Ra and is unable to escape because of the noose Phiri Dun-Ra places around his neck as Phiri slowly siphons his abilities. It is revealed Mark is being controlled by another Mogadorian. After Mark gets a chance to break free and tries to stop her, Phiri Dun-Ra stabs him under his jaw, killing him.
|“||Your dad's a good guy, we might have to make him an honorary Cêpan||”|
–John to Sam, about Malcolm
Malcolm Goode is John's best friend Sam Goode's father. When John and the other Loric arrived on Earth, Malcolm was there to greet and help them. John learns about it in a letter Henri leaves for him. John meets him again when he goes to find Number Five in Arkansas. He becomes a sort of an adopted Cêpan for John and the remaining Garde. He helps them learn more about the contents in their Loric chests and helps them train, too. When Mogs invade Nine's safehouse, he defends John and Ella who are comatose. He gets badly injured in the process and nearly dies. John heals and saves him since he didn't want Sam to go through what he went through with Henri.
John and Marina have only known each other for so long, but some kind of relationship has developed. When Marina first meets John, she's amazed that she's finally met the famous "John Smith." John is equally amazed by Marina's healing Legacy. John also states that he really wants to take the time to get know her, but they are in the middle of the Battle of Dulce. Later on, when John runs to Ella and Sarah's aid, Marina is able to identify John's new healing Legacy. It can be assumed that after the battle, Marina helped John learn more about his new Legacy.
While in Chicago, John and Marina seem to develop a brother/sister relationship. While in the kitchen, Marina asks John if they should establish a cleaning and cooking schedule for the apartment, with John agreeing. The two of them often work together to help Ella. They face off in Capture the Flag, in which Marina beats John by using Nine's Legacy to run up the wall. It can also be assumed that Marina looks up to John for battle tips and she sees him as a leader
Once John is put in a coma by Ella and Marina leaves for Florida, their friendship is on hold until they reconnect.
When they reunite at Ashwood Estates, they embrace and hug once again before Marina leaves for Mexico. In the aftermath of Mexico and Sarah's death, John and Marina became closer as Marina understood the pain John was going through and his need to keep moving and fighting. At the end of United as One, John finds Marina. Marina shows him how Five is doing. Afterward, John takes her back to the Himalayas to show her what he's been doing after their one year apart and they share a kiss. In "return to zero" It is said that the relationship between Marina and John is unknown therefore there is a chance they might be together.
|“||I made a choice, they won't hurt her.||”|
–John about Ella
In I Am Number Four, John sees a vision of Ella as a baby escaping Lorien during the invasion in a second ship with three Cêpan and some Chimæras. John meets Ella physically in The Rise of Nine. She is nearly killed along with Sarah by the Mogadorian leader, but John saves them both with his newly developed Healing Legacy. When Ella experiences nightmares after escaping from Dulce, he talks to her and shares his own experiences about the visions of Setrákus Ra. When Ella falls into a coma, she pulls John into her dream and puts John in a coma too. In the dream, John finds out that Ella is Setrákus Ra's heir. When Mogs kidnap Ella, instead of rescuing her John decides to save Malcolm who is seriously injured and is at the verge of death. In The Fate of Ten when John realizes that Ella is connected to Setrákus Ra he is reluctant to kill him as it would mean killing Ella. In United as One when Ella reveals that she foresaw Sarah's death John becomes angry, but tries to hide it.
|“||All right Adam, you're gonna help me win this war.||”|
–John to Adam, The Fall of Five
Upon initially meeting Adam, John is reluctant to trust him due to Adam being a Mogadorian. When Adam kills his own father to save Four's life he begins to lose his distrust of Adam. During United As One, John trusts Adam enough to destroy the West Virginia Mogadorian Base in the final battle even if it means killing him and the others. Later John meets up with him in Alaska and gives him a Loric pendant with the power to transport Adam back to the Himalaya base that John has made his home.