Kai is Nya's older brother. Growing up, he was the only family she had following their parents' disappearance because of that the two are very close. It was Nya being kidnapped that Kai became a ninja as he wanted to save her. Kai was the first ninja to find out about Nya being Samurai X and agreed to keep her secret after she stated her reasons.
Is Nya and Kai's father who disappeared sometime after her birth. Having been very young at the time of his disappearance, Nya has vague memories of her father but like her brother, she wished to find out where and why he left. In Hands of Time, she and Kai realize their parents are alive and were confused by Krux's declaration of them being traitors. When she and Kai come face to face with their parents, she is welcoming of them but her brother is less forthcoming. Nya the learns that her parents were forced to her the twins after Krux threatened her and Kai when they were young.
Is Nya and Kai's mother and the one who she inherited her elemental powers from, she disappeared sometime after Nya's birth. Being very young at her disappearance, Nya has vague memories of her mother and does not how mothers treat their child. In Hands of Time, she and Kai realize their parents are alive and were confused by Krux's declaration of them being traitors. When she and Kai come face to face with their parents, she is welcoming of them but her brother is less forthcoming. Nya the learns that her parents were forced to help the twins after Krux threatened her and Kai when they were young.
Since the beginnings of the show, Nya has carried a romantic relationship with Jay which has been put under stress on several occasions. She and Jay were clearly mutually attracted to one another until "The Surge," when her perfect match was revealed to be Cole. Later, after she became the Master of Water, Nya has distanced herself from the former, insisting there was nothing remaining between the two and they were simply friends, much to Jay's disappointment.
However, by the end of Skybound, when Nya was dying due to poisoning, Jay saves her by undoing all of Nadakhan's actions. In the finale, she reconciled with Jay and they share a kiss.
Nya and Cole are good friends but in Season 3, she discovers that Cole is her perfect match. Following this revelation, she grew awkward around him though developed an attraction to his kind nature which soon initiates a rivalry between Jay and Cole who compete for her affections. In Season 5, she comforts him when he becomes a ghost and helps him gain some encouragement from his new circumstances. In season 6, Nya chose Jay over Cole who accepted this with a smile but this doesn't cause a rift between them as they remain good friends. When Cole returned to being human, Nya was happy to see him back to normal and hugged him with the other ninja.
Wu is the Sensei of the ninja, she gets along well with as it was thanks to that her brother was able to save her from Garmadon. Though not a ninja in the first four seasons, Wu and Nya were shown to get along and he was able to impart wisdom into her whenever she felt left out of the ninja's activities.
In Season 5, Wu informed a surprised Nya that she was the elemental master of water and started to train her in the usage of her power to become a Ninja. Nya is now one of Wu's students along with her brother Kai.
In Season 7, she ninja come to his aid when he fights Acronix by himself. She later saves Wu from succumbing to the effects of the time blades with Wu back to normal, he helps them foil the time twins plan. He later aids Kai and Nya battle the Time Twins but when the villains prepare to finish the two ninja off, Wu sacrifices himself to save them. Though happy at their victory, Nya couldn't help but be worried when her master is feared lost in time with their enemies.
Nya and Zane get along very well and are friends throughout the series. In season 4, Nya is sad about Zane's "death" but when searching for the other ninja she is surprised that she detected Zane's recon beacon which gave her a clue as to where they were located. When she finds the ninja on Chen's Island, she immediately runs to hug the newly rebuilt Zane relieved that he was back.
In Season 6, Nya was worried when Zane disappeared because of Nadakhan and feared the worst. After Nya was struck by Tiger Widow venom and succumbed to the poison, Zane was sad at her death but fortunately these events were undone due to Jay's last wish.
In Season 7, when Zane is attacked by Krux and Acronix, she works very hard to restore him after he is unconscious for a while. Nya was successful in awakening Zane and was relieved to have him back in action.
Lloyd and Nya are good friends, though they don't interact much in the series. Nya and Lloyd do show that they care about each other. In Season 4, when Chen's army was about to invade Ninjago, Lloyd volunteered to go alone and Nya expressed worry for him to take on such a large task by himself.
In Season 5, she wanted to help save Lloyd when he was possessed by Morro and was relieved to see him released from the evil ghost ninja. In return, Lloyd was happy with the new addition to the team and congratulated Nya for unlocking her true potential and defeating the Preeminent (even though it led to his father's demise).
She and Dareth get along well though she is put off by his tendency to showoff. In Season 4, he accidentally travels with her to Chen's Island much, to her annoyance but he proves himself helpful as his talent in the art of disguise aided Nya in infiltrating Chen's palace and find out his plan.
In Season 5, Nya met Ronin when her friends accidentally gave him a share of their tea shop. Ronin didn't mind telling Nya he was in debt to the Soul Archer and helped Nya with her training by giving her advice of not caring too much. When Morro and the other ghosts force Ronin to tell the steal the Sword of Sanctuary, she impedes him, forcing him to fight her since he needed to repay his debts to the ghosts. During the fight, she sees a future of him kissing her, which causes her to kick him in the leg in disgust as he questioned it but she replies he knows what he was going to do before he takes the sword. She is disappointed when he hands it over to Morro but is relieved when he helps them fight the Preeminent.
Nya met Harumi when she and the others were assigned to protect the Royal Family. For unknown reasons, Nya wasn't particularly impressed with them, but she was respectful to Harumi in their first meeting. When Harumi referred to her simply as the girl of the team, Nya was obviously annoyed but that soon changed when Harumi voiced her admiration for her and stated she wanted to be like her ever since Nya became proud warrior and master. Flattered, Nya smiled and stated she liked Harumi.