That sounds very cool and I really like that idea. The only thing is I don't know if Regis would focus on one child over the other and not give his daughter (I was imagining an actual biological girl as this is based on other fics for other fandoms I've seen where the character was transported back to the beginning but as a girl) combat training since from what we know of Lucian royalty there were queens who fought and Regis seems to a rather modern king if he is willing to put his kid in public school and let them live alone (within reason). Also interesting to see Noctis adjust to now being an older sibling and who would the kids mom Aulea or a second wife?