Kyo had an unsteady childhood and a rather rough family life because of his curse. Normally, parents of the juunishi either can't stand their cursed children or they become very over-protective of them. For Kyo, his true form was so horrifying that it would be hard for even the most over protective mothers to come to terms with as was the case with Kyo's mother, who always seemed protective of him when he was a child. She claimed that she loved him, but Kyo knew deep down that she didn't really because of how she refused to acknowledge his "true form". Kyo's mother was afraid of him. She would constantly check to see if Kyo was wearing his bracelet and she refused to take him out into public, telling him that she thought he was so cute that she didn't want to share him with the rest of the world. She would constantly shower Kyo in hollow praises of affection. Kyo always wondered if his mother was ashamed of him because he was possessed by the spirit of the cat and that his mother didn't want others to know about him. Kyo's mother, in despair over having her son born a 'monster', committed suicide by walking in front of an oncoming train (Volume 21, Chapter 119) when he was a young child of possibly four to six years old.

After his mother committed suicide, Kyo's father blamed the death on him because he was the cursed cat, so Kyo's father disowned him. He refers to Kyo as "it" and believes Kyo to be a demon that deserves to be locked away in eternal darkness. In volume 15 of the Manga, Kyo's father is seen blaming Kyo on all of the bad things that had happened to him. He also makes a brief appearance in volume 6, saying to Kyo "Your mother loved you more than anyone!" Towards the end of the manga, Kyo makes an effort to reconcile with his father, but was violently rejected by the man. It was during this confrontation when Kyo realizes that his father had shunned his mother in addition to him, hinting that his mother committed suicide because of her protectiveness of Kyo. Kyo sees how pitiful his father was in blaming everything on him and decides to leave. Whether he reconciled with his father by the end of the manga is unknown.

People have criticized Kyo throughout his life for his differences, too frightened or never bothering to glance beyond the label of 'The Cat' and regard Kyo as a true person. Like most of the Sohmas, throughout his school years, he begins to get picked on for the color of his hair but he would chase them around, threatning to kill them, which was around the time his temper began.

The only person Kyo has ever truly known as family is Souma Kazuma, a martial arts master who owns a dojo where Kyo, Kagura, Yuki and Hatsuharu learned martial arts. Kazuma's grandfather was also cursed with the cat and is the one person who really understood what Kyo went through. He himself was one of the people who shunned his grandfather out of ignorance and to make up for it, Kazuma adopted Kyo when his father rejected him, accepting the responsibility due to guilt over past wrongs he did and because he was the only one who had any inkling of what Kyo was going through. The name of Kazuma's grandfather is unknown. Kazuma made Kyo feel as if he was loved and thus improved Kyo's life very much. In return, Kyo loves Kazuma like a father. Kazuma once talked about the "old Kyo" who used to blame all his problems on others, but Kyo is now able to face them. Kyo learned martial arts from Kazuma, calling him Shisho ('Master').

For a while Kyo had issues with Kazuma over his role as father. Kyo despised that others thought Kazuma was weird for raising a cursed child. Because of this, Kyo claimed Kazuma wasn't his father, as he didn't want Kazuma to be hurt by his cursed existence. However, Kazuma felt like a father and in fact desire to be accepted as Kyo's father. But when he heard Kyo's reaction, Kazuma distanced himself because he didn't wish to force his feelings upon Kyo. Eventually, this misunderstanding was resolved with Kyo's transformation.

Kyo no long lives with Kazuma because he wanted Kyo to live at Shigure's house where Tohru acts as the housekeeper, and so that Tohru could continue giving him the "healing effect". Kyo still visits the dojo where he and Kazuma trained three times a week.

Kyo is cursed by the cat, an animal not in the Chinese zodiac but which legend says would have been if it had not been tricked by the rat into missing the induction feast. As the cat, Kyo hates Yuki, the current rat of the zodiac, who he sees as never having to work hard at anything, and has dedicated his life to defeating him. Shortly before the series beginning, Kyo made a bet with Akito: if he defeats Yuki before graduating high school, he would officially be accepted as part of the zodiac; however, if he does not, Kyo would be confined inside the Sohma estate for the rest of his life. Despite many months of strict training, however, Kyo never lands a decent blow on Yuki. Kyo is fiercely competative, and can be easily manipulated into doing things he does not want to by turning it into a competition-especially against Yuki. Kyo is also really competitive with Yuki. He will get in a argument or a fist fight, but Yuki always has a comeback or beats him. He even ends up having to live with Yuki. Both of them have a crush on their housekeeper, Tohru, which leads to a lot of problems in their house. Their rivalry distresses Tohru, who likes them both, but she comes to worry even more when they do not fight. The two eventually tell each other, during an argument, they envy as well as despise each other and come to a truce for Tohru's sake.