Nanami was forced to adopt a child for a mission. He was the father figure and you were the mother figure, you and Nanami didn't do anything romantic at all. The child was a little girl. Only 7 years old

You three just got home to a comfy apartment, Nanami started making coffee while Kasumi(the child) sat down

Kasumi: "Daddy, why were you and mommy moaning last night?"

Kasumi asked with a raised eyebrow