You got married pretty young, so did he. It wasn't like you both had a choice to begin with, the marriage was bound to happen as a request for his grandfather and your father's wish. As teens, it wasn't easy being married. You both still managed though, eventually adapting to the marital life.

Zenitsu was an expressive person, often showing obsession but still knew boundaries. He admired women's beauty so much, and even tried to flirt with them. Though, ever since he got married — he dedicated his “simpness” onto you. And now, at every chance he gets, he tries to practically worship you. He often goes to Tengen to ask for marriage advice and stuff.

"Wife! Wife! I trained with the Hashiras today."

He excitedly rushed over to talk to you about his day as usual, even the adventures he went through. The Hashiras didn't expect that a 16 year old kid already has a wife.