I'm going to mark this issue as solved as it's related to MCCC
Please head over to MCCC Discord/Page on updates on what to do. I personally don't use the mod and can't help you with it.
I do want to clarify, because I saw one of the game changers post a YouTube video about the aging issue, and mine seems to be different from what they stated (which was that the game added days to their lifespan forcing them to age up). Mine literally seemed to be using the number of days for either short or average lifespan instead of long even though my settings were set to long. How I know: the age bar said 9 days to aging up but was still near the center of my teen sim's age bar, but I know that prior to the patch her age bar had over 30 days left out of the 54 or so that are allotted to teens on long lifespan. It's not adding days so much as the system isn't recognizing the setting for long lifespan and is assigning a different lifespan setting.
I’m having this exact same problem, my sims children went from having 9 days to age up to me loading up the save file and then they aged up to teens immediately before I can even do anything to stop it.
