Despite their mutual affection for each other, Kiara and Simba initially had a strained father-daughter relationship, due to Simba's overprotective nature, and Kiara's insecurity of becoming future queen, she yearned to prove to her father that she was responsible and mature, and despairs when Simba breaks a promise to her to the point she tried to leave the Pride Lands, she became more distant with her father after spending more time with Kovu whom Simba distrusts due to Kovu's Outsider heritage. This further worsened after Simba banished Kovu for the crime that she believes Kovu is innocent of (which is true) and confined her to her den to make sure she won't meet him.
Kiara was disappointed by her father's irrational decision, and disobeyed his orders to find Kovu, however, Kiara still loves her father and cares for his well-being, so she convinced Kovu to help her reunite their prides and help her father realize Mufasa's true wish. After the two prides are united, Kiara fully reconciles with her father with Simba finally accepting that she already mature enough to be assertive and make her own decision.
In The Lion Guard, Kiara has a friendlier relationship with her father, happily learning how to become a proper queen from him.
Kiara's and Nala's mother-daughter relationship is observed to be affectionate and supportive, Unlike Simba, Nala isn't overprotective of her daughter, and shows trust in Kiara's abilities. She expressed support and pride for her daughter on the onset of her first hunt and was relieved that Kiara was unharmed by the fire set by Nuka and Vitani. Nala also supports her daughter's blossoming romance with Kovu, an outsider, as shown when she suggested Simba to get to know Kovu and shocked when Simba exiled Kovu out of rage. She was greatly relieved when Simba admitted he was wrong about Kovu and allowed him to rejoin the pride, knowing the happiness this brought to Kiara. With great pride and joy, Nala happily watches and takes part in her daughter’s wedding to Kovu, roaring alongside them over the Pride Lands.
In The Lion Guard, Kiara is shown to have a loving mother-daughter bond with Nala, more or less the same as in The Lion King II: Simba's Pride, and enjoys learning about the importance of hunting and tracking from her.
Kiara has a common sibling relationship with Kion, her younger brother. Both occasionally prone to sibling rivalry due to her arrogance and immaturity that is opposite of Kion's more sensible and responsible nature, but still hold affection for one another in the end. Unlike their great-uncle was with their grandfather, Kion doesn't hold resentment or jealousy towards his older sister's role as future queen, even when she bossed him around while acting as interim queen, and realized that as her younger brother he needs to be by her side to support her and give her the right advice especially if she's wrong.
In "The Trail to Udugu", Kion and Kiara's sibling's rivalry is made apparent as both were trying to best one another to find Udugu, which only resulted with them messing up. Only after their mother went missing did Kiara and Kion finally acknowledge' each other's skills and learn to work together and found their mother. While their rivalry is still there, the two siblings are on much better terms than before.
Throughout the rest of the series, Kiara and Kion become much closer to Kiara serving as a source of support to her brother. He and The Lion Guard also come to her rescue a number of times as well. Kiara also develops more respect for Kion’s duties leading the Lion Guard, as she strongly disapproved of Tiifu and Zuri wasting the guard’s time with a minor emergency.
In ”Battle for the Pride Lands“ Kiara was deeply worried about Kion after he got his scar. When Kion learned that he had to journey to the Tree of Life in order to have his scar healed Kiara wished him luck as he departed. Kion, in turn, wished to return in time to see his sister’s first hunt.
Many months later in “Return to the Pride Lands“ when Kion returned from his journey he was delighted to see Kiara again and when he thought she was in danger from Kovu (due to not realizing the events that happened while he was away) he quickly attempted to protect her before she explained everything to him.
Later that night Kiara and Kion sat together watching the stars from Pride Rock. Kion confessed to her how seeing her together with Kovu reminded him of a certain “friend” he met at the tree of life. Realizing her brother’s feelings for his so-called friend, Kiara teasingly expressed delight over the fact that Kion had a love interest of his own, and wished to know about her. She was impressed when it was revealed to be Rani, the Queen of the Tree of Life. Sensing Kion’s sorrow, she realized that he missed Rani and was longing to be with her again. Knowing full well the pain of being separated from the one you love, Kiara consoled Kion, assuring him that he would be able to return to her, with the approval of their parents.
Kiara later attended Kion and Rani’s wedding/coronation ceremony along with Kovu, Simba, and Nala. During the event she enthusiastically cheered for Kion, overjoyed that her brother, like her, was able to be with the one he loves as well as becoming a ruler himself.
Due to his death, Kiara never got to meet her grandfather. She knows how honorable he is when she defies Simba after banishing Kovu saying that Mufasa never would've done something as selfish as that.
In "Return to the Pride Lands" she and her family were shown speaking to Mufasa's spirit.
Kiara wasn't born when Scar was killed, but she knew about the horrible things he did as a false king. When he returned from the afterlife, Kiara was determined to help Kion and the Lion Guard defeat him.
In "Battle for the Pride Lands" after escaping a fire from Pride Rock, Scar appeared before the royal family and Kiara showed signs of fear upon seeing her great-uncle.
Vitani originally hated Kiara, since she was a Pridelander and the daughter of Simba, the Outsiders’ most hated enemy. At first, Vitani held no respect for Kiara, viewing her as nothing more than a mere princess and Simba's "pretty daughter". It was Vitani along with her brother Nuka who set the flames to trap Kiara so Kovu could rescue her and thus infiltrate the Pride Lands in order to assassinate Simba. However, when Kiara and Kovu worked together to stop the fighting between the prides and pleaded for them to join together again, Vitani was deeply moved and became the first Outsider to rejoin Simba's Pride.
When Vitani did this she openly admitted that Kiara was right, thus developing a newfound respect for her, and acknowledging her wisdom. After her mother’s death, Vitani smiled as she watched her brother marry Kiara; making them sisters-in-law. Kiara, in turn, happily accepts her mate’s older sister as a member of her family.
When Kion returned from the Tree of Life and was about to use the Roar of the Elders on Vitani and her Lion Guard (due to believing them to still be enemies) Kiara risked her life to protect Vitani by jumping in front of her brother before he could use the roar. This shows that both Kiara and Vitani completely accept each other as family, and have grown to care for each other. Along with the Pride Landers, Kiara cheered for Vitani when she became the official leader of the Lion Guard.
Kiara and Rani are on good terms. She along with Simba, Nala and Kovu attends Rani and Kion's wedding; making Rani Kiara's new sister-in-law. Kiara enthusiastically cheers for them along of the rest of the Pride Landers.
Kiara and Baliyo are on good terms. Baliyo becomes Kiara's brother-in-law when Kion marries Rani.
Kiara first met Kovu as a cub when she disobeyed her father's order and entered the Outlands. When she first met, Kiara was wary of Kovu, but she immediately loosened up to him and admires his way of living without relying too much on anyone. They quickly became friends after working together escaping from a group of crocodiles, but soon were separated by their parents due to their hatred for one another. Even though this was their only meeting, it leaves a big impression on both Kiara and Kovu.
When they're reunited years later, Kiara soon recognizes her childhood friend and is more than happy to welcome him into the pride after he saved her from the fire (which was actually part of Outsiders' plan to get close to Simba) Kiara begins to spend more time with Kovu, having him teach her how to hunt and she in return teach him how it feels to simply have fun. Her feelings eventually blossomed into love. Even after hearing Simba's accusation of Kovu led him to the trap to kill him that results with Kovu's exile, Kiara still believes in Kovu's love for her and pleads to her father to reconsider his punishment while defending Kovu. Her love for Kovu is so strong that she disobeys her father's order to look for him, showing how much she wants to be by his side. After they are reunited and convinced their prides to stop the fighting, Kiara and Kovu are finally married.
Tiifu and Zuri are Kiara's best friends. They enjoy learning how to hunt together and usually spend most of their days together. Tiifu admires Kiara as the princess, expressing excitement and strong faith that Kiara will do great when they learned how to hunt together. She's also jealous of anyone that she thinks to be too close to Kiara, which is shown when she saw how Kiara and Fuli trained to hunt together, thinking that Fuli is trying to replace her position as Kiara's best friend. While Zuri doesn't go as far as Tiifu, she also admires Kiara and believes in Kiara's capabilities as future queen and takes her duty seriously when she's tasked as Kiara's royal adviser.
In "Baboons!", Kiara tasked Tiifu and Zuri with helping her prepare for her royal duty, she expresses amused annoyance with their obsession with her appearances, but later credits them when speaking to Vuruga Vuruga.
In "The Underground Adventure", Kiara immediately saved Tiifu without a moment's hesitation when she accidentally caused a cave-in during a panic attack, proceeded to berate Zuri and Bunga for causing her fears to manifest even further, and comforted Tiifu until they returned home, indicating that despite showing annoyance for their prior act of getting the Lion Guard involved in a false alarm, she still sees them as friends.
Despite their differences, Kiara is shown to have a close relationship with her father's childhood friends and guardians. She expresses annoyance at Simba's insistence that they accompany her everywhere, but still maintain a good relationship with the both of them. Timon and Pumbaa were initially shocked and disappointed when they found out Kiara is a girl as they had expected to raise her as they did with Simba, but eventually accepted her since she's Simba's daughter. They take their duty as Kiara's guardians seriously and make sure she's not hurt whenever she's going out alone, though unfortunately they constantly lost her due to their clumsiness.
Kiara becomes good friends with queen Dhahabu when she visits the Pride Lands.
Kiara appears to have a friendly relationship with her father's shaman, Rafiki was the one that Mufasa foretold Kiara and Kovu's eventual romance to, and though he was skeptical of the plan, Rafiki agreed to bring the two together for the benefit of the prides. When Rafiki surprised Kovu by appearing suddenly in front of him, Kiara calmed a panicked Kovu by saying awkwardly, that he was a friend of the family, indicating that despite not knowng him personally well, she still saw him as a friend. He sang Upendi in order to boast their blossoming romance. This led to Kovu and Kiara reuniting after Kovu's exile, and joining together to save their families and prides.
After the battle, Rafiki blessed their union, and watched as Kovu and Kiara nuzzled each other and roared from atop the peak with Simba and Nala.
Like her relationship with Rafiki, Kiara is also shown to have a close friendship with Simba's majordomo. He helped her father warn her about the dangers of the Outlands, and the Outsiders, and during her first hunt, Zazu located her and led her parents to her location. After the battle, Zazu watched as Rafiki blessed Kovu and Kiara's marriage.
Kiara and Janja used to be enemies. Janja dragged Kiara into the Outlands twice. However Kion's guard saved her. In "Battle for the Pride Lands" Kiara and Janja become on good terms.
Kiara and Anga are on good terms. Anga saves Kiara when Pride Rock was on fire.
After being lost under ground Kuchimba helps Kiara and her friends get back home.
Zira dislikes Kiara since she's Simba's daughter. Kiara falls in love with her son Kovu. Kovu and Vitani decide to join Simba's Pride and Zira got mad. Zira tries to attack Simba one last time but Kiara stops her. Zira hangs on to a cliff and Kiara tries to save her. Zira falls to her death and Kiara marries Kovu, thus making Zira Kiara’s posthumous adopted mother-in-law.