What are you talking about? All Perv has to do is rewrite the revelation scene so that Nadya says that Aven was born first then Cam. Or he could just ignore the fact Nadya said she was the middle child and have future chapters treat Aven as the older one. This isnt a Nayda lied issue, this is a writer forgot something they wrote earlier so they made an accidental retcon. Rewriting the older chapters to say Cam is older or rewriting the last revelation scene to say that Aven is older would have the exact same effect. So does pretending like Aven being older or younger wasnt mentioned before. It's not a thing about any character lying it's just a minor mistake that can easily be corrected. It's really not nearly as big a deal as you are making it out to be. It really just boils down to whether or not you prefer Aven being older or young. I just prefer if she was older, I feel like it would make the dynamic better and make more sense as to way Augst didnt want her.
I also dont think it would be that much work to rewrite the recent convo. It was only one conversation it's not like he had multiple plot threads around Cam being older. The fact that this revelation is so recent is why it's an easy thing to fix
lol of course I'm aware this is a minor mistake, I just chose not to mention it that way.
The mention of "could Nadya be lying to MC?" just popped up in my mind because someone before you asked in another reply "Could Nadya have been lying to Aven about her age?" which I think is unlikely (given her character), and thought the same regarding her interaction with MC (nothing more, nothing less).
Just have a feeling Perv is taking the MC-Nadya convo which was released in recent update as the canon path than what was mentioned/narrated by MC (or Aven) regarding their ages.
As to which fix is easier, well my personal subjective opinion would probably be the fix to 1 or 2 words in few previous scenes, but I do admit I'm not expert regarding how this all works, and was just basing it purely on assumption.
Tbh, I don't mind even if MC is a little bit older than Aven (or vice versa).
As I said before, some people act more mature depending on the environment they grew up in, and I can see Aven being that way despite being younger than the MC.
I don't think her age (whether she becomes older or younger) influences her dynamic with MC (and others) at all, given we already know how Aven generally acts/behaves. If it does, I feel it's a very minuscule effect (I feel the change from cousin to sister would probably be bigger influence than the age number).
But if you feel differently/disagree, then that's fine. All subjective opinions & different strokes for different folks.
In the end, it's gonna be up to Perv where he adjusts it in the next update (whether older, or younger).