The relationships of Kovu from The Lion King franchise
Despite the harsh conditions of their environment, and the pressure of Kovu's status as Scar's chosen heir, Kovu appeared to have a decent relationship with his mother during his cubhood. He appeared to harbor affection towards her, and strived to please her. Zira used Kovu's newfound friendship with Simba's daughter, Kiara to formulate a plan that'll set Kovu onto the throne of Pride Rock. However, when Kovu sided with Simba out of love for Kiara, Zira believed he had been corrupted, and said he had betrayed her and Scar's memory. Zira's deriding insults then caused Kovu to declare he wanted nothing more to do with Scar or his mother's vendetta. When Zira was about to fight Simba one on one during the final battle between Pridelanders and Outsiders, Kovu defied her, saying he wouldn't let her hurt Kiara or Simba while he breathed. Despite this estrangement, Kovu still loved his mother and when she fell to her death, he mourned for her.
Kovu appeared to have a close sibling relationship with Vitani. They appeared to be close in age, and presumably played together as cubs. Before Kiara's first hunt, Nuka and Vitani set the Pride Lands ablaze in order for Kovu to rescue Kiara. Later, as Vitani spies on Kovu, she discovers his betrayal and hurriedly goes to inform Zira. She takes part in the battle between the Pridelanders and the Outsiders and watches as Kovu and Kiara confront their parents, Vitani is moved by their apparent affection for each other, and the truth in their pleas. She defies Zira and moves over to stand beside Kovu. She presumably watches the marriage of Kovu and Kiara, and roars alongside the combined prides.
Much like Scar's resentment towards Mufasa, Nuka harbored an intense hatred and sibling rivalry towards his younger brother for his position as Scar's chosen heir, and the apparent favoritism that Zira gave him. However, Kovu held love for his brother, as he defended him against Zira's accusations and was saddened by his death.
After hearing about the dangers of the Outlands and the Outsiders from her father, Simba, Kiara decides to venture into the forbidden territory, where she bumps into Kovu. After a brief confrontation, Kovu and Kiara are ambushed by a float of crocodiles. They mange to escape and formally introduce themselves, Soon Simba and Zira arrive and after a brief confrontation, they take their children back to their respective homes.
Months later, Kovu's siblings Nuka and Vitani set the Pride Lands ablaze during Kiara's first hunt, Zira sends her son into the mist of the flames to rescue Kiara. After reuniting, Kiara was pleased to see her cubhood friend. Their reunion was interrupted by the arrival of Kiara's parents, who greeted their daughter with relief. After a brief confrontation with Kovu, Simba initially refused to allow him to join the pride. He changed his decision after Nala and Zazu reminded him about the law set by Mufasa, and begrudgingly allowed Kovu to come to Pride Rock. As the days pass, Kovu and Kiara begin to spend time together, and their friendship blossoms into romance. With help from Timon and Pumbaa, Kiara shows Kovu the concept of fun, and they stargaze later that night. After Simba requested to speak with Kovu, Kiara was delighted and watched as the pair exited Pride Rock. Later, Kiara expresses shock at Simba's claim that Kovu was involved in an ambush set by Zira and heartbreakingly watched as Simba exiled Kovu. After Simba confined Kiara to her den, she escaped and ventured away from Pride Rock to find Kovu. After they found each other, Kiara convinced Kovu to return to their prides and rescue their families.
After the battle, as Rafiki blessed their union, Kovu and Kiara nuzzled each other and roared from atop the peak with Simba and Nala.
Initially, Kovu had a rocky relationship with Simba. Simba mistrusted Kovu due to his outsider heritage and status as the adoptive son and chosen heir of Scar. After reuniting with Kovu, Simba became distrustful about Kiara's growing love for the Outsider, and initially refused to allow him to join the pride. He changed his decision after Nala and Zazu reminded him about the law set by Mufasa, and reluctantly allowed Kovu to come to Pride Rock.
Simba eventually starts to trust and warms up to Kovu, unfortunately, this trust was completely destroyed, when Simba was ambushed by Zira and her pride, the latter claims that Kovu led him into an ambush (which was a lie) due to his gullible nature, Simba believes it, Kovu tries his best to protect the Lion King, but he was knocked out by his sister, Vitani, before he had a chance to do so.
When Kovu returns to Pride Rock, he tries to convince Simba that he had nothing to do with the attack on his life, as well as the fact that he had no knowledge of the ambush, unfortunately, Simba was too blinded by his anger to listen, as he wrongfully/unfairly banishes Kovu from the Pride Lands for life, despite the fact that he nothing to do with the attack on Simba's life, the latter accepts his exile, and is sad that he has lost his friendship with Simba.
After intervening alongside Kiara to stop the fight between the Outsiders and Pridelanders, and showing that he won't let Zira hurt her or Simba, Simba comes to realize that he was wrong about Kovu and accepts him back into the pride. He then allows Kovu to marry Kiara and begins grooming Kovu as his successor to rule alongside Kiara.
Kovu and Kion met in the Outlands sometime after he met Kiara. They did not interact much together but Kovu had no hostility towards Kion during the events that followed after their meeting.
After Kion is used the Roar of the Elder to drive the Outsiders to another part of Outlands, Kovu who had narrowly avoided the roar, looks towards Kion who glowers at him. When he moves a step towards him, Kovu runs.