(AUTHER: SORRY BUT THIS MIGHT SPOIL THE STORY, I JUST WANT TO PUT THE FAMILY TREE SO YOU UNDERSTAND THE FAMILY TREE)
Birth mother: Hana Naneko
Hana Naneko married Akam Haruno which brought the pink hair and eye color changing into their child's bloodline(Naneko blood), after giving birth to Kai she died 1 year later by going on a mission with Minato's team which caused her and Obito to get crush by a rock,but with Obito being half dead and her being fully dead and Kai now was given the Naneko wolf jutsu and the 11-tails wolf, but to be honest that did happen but at that time it was Sakura's mom that killed them
Akam Haruno
4 years later, Akam Haruno remarried Mira Mikist and had Sakura, but Sakura was born with yellow hair so Mira died Sakura's hair permanent pink like Kai's hair but his was in his jeans, because of the pink hair the two kids were known as twins so thats what they were now known as. And they even started the academy together even though Kai was 5 years older he was put in the prodigy class.
Mira Mikist
Sakura Haruno