I'm trying to recall a fic where Nodoka finds out that Genma had made multiple engagements for Ranma, including Kaori Daikoku and Picolet Chardin.
She decides the main way to deal with it is to have Genma produce more sons and a daughter for Picolet. She drags Genma back to her home to start fulfilling the duty.
For some reason Genma is shown to be reluctant to fulfill this duty, and I think it was implied that Nodoka was a bit of a dominatrix and a sadist, which was one of the main reasons Genma took the 10 year training trip to get away from his wife.
I'm not sure about that, I could be conflating two separate fics where the dominatrix Nodoka was the reason for the training trip and her deciding Genma needs more children for the arranged marriages being a completely separate story.
So does any of this ring a bell for anyone? I've been mostly reading other fandoms for the last decade, so it's probably something at least 10 years old.