Nagisa would be the one to bring up wanting a kid first, and then begin hinting at it whenever Rei was around and he could make an implication. I can see him being excited at the thought of being a dad, based on how he wanted to play with the kids and, you know, how impressed he is by Rei’s ability with them
But Rei is not as ready as Nagisa. He will overthink their decision a thousand times because he wants to make sure he will be the perfect father and be capable of raising his children in the best conditions, and wants to read every parenting book so he is prepared for any ailment or crisis that will come between their children and a healthy, happy life. Rei will take this all very seriously and it will be a while before he finally realizes he has to take a leap of faith, and will never be fully prepared. And Nagisa will be thrilled when he finally says yes.
Nagisa decorates the baby’s room using Pinterest inspiration and blind leaps of artistic faith, and Rei takes care of stocking up on supplies. They both overdo their budgets significantly.
Rei will mostly be the one who wakes up in the middle of the night for the baby, because Nagisa is usually out like a rock. When the baby gets its first rash or fever, Nagisa will be the one to break down first so Rei will pretend he’s not freaking out until the doctor assures them the child is fine, and then he’ll cry with relief.
Nagisa lets the child sleep in the bed with them when they ask, and at first Rei objects, insisting that every parenting book advised against allowing the child in the bed at a young age. Nagisa and the child pout and plead until he relents. When the child outgrows the habit, Rei’s actually the one who misses it the most.
That’s around the same time Nagisa talks Rei into having a second child.
Nagisa is the parent that goes to social events, PTA meetings, and makes sure any historical reenactment projects the kids are assigned outdo the other students by a mile. Rei helps the kids study and helps them sort through conflicts they have socially at school. The kids prefer Rei’s cooking and Nagisa’s movie selection. They go to Nagisa when they need a “yes” to something and Rei when they need an answer.
Here’s for a third season about Rei and Nagisa’s married life