BuT CJ, MrS. aFtOn IsN't EvEn In ThE gAmEs! WiLlIaM cOuLd'Ve JuSt AdOpTeD hIs ChIlDrEn! As some people would say. Well then, let's go into how Mrs. Afton's existence itself would have to be possible in order for a key character to make sense.

And where is my proof for this, you may ask? In the games themselves. But not in the way that you would expect it to be. Yes, I don't see why people haven't talked about this more in detail, but one day, I realized something very key that could make Mrs. Afton's existence proven.

That proof is actually an important character of FNAF: none other than Michael Afton.

What does he have to do with this? Well, in Sister Location's Custom Night ending, I have all the evidence I need for my claim. Watch through it once. PAY ATTENTION TO IT.

What did you notice? The two key things are these: "They didn't recognize me at first, but then...they thought I was you." And the second thing is Michael's voice in general.

Why is this important? Well, I think I need to point out that PJ Heywood is the voice actor for BOTH William and Michael Afton, first of all, meaning that both of them should sound very familiar with one another. And second, if the Sister Location animatronics did indeed mistake Michael for his own father, then he would have to look a lot like him. Which I doubt would've been the case if he was adopted. Why is that? Because of two words I have for you:

GENETIC INHERITANCE

That's right. You weren't expecting a biology lesson, were you? Well, too bad!

Basically, each parent gives their children each half of their genetic material to their children, and that combination makes genetic traits in their children. If Michael is supposed to look and sound exactly like his father did, then William would've had to have a wife, or a female mate in general, to produce a biological offspring with his own genetic traits passed onto Michael.

Unless you are willing to argue that somehow, out of the entire random luck of the universe, that Michael is adopted and just happens to grow up looking and sounding exactly like his father without actually being genetically related to him, please tell me the odds.

BUT HEY! THAT'S JUST A THEORY! A GAME THEORY! Thanks for reading!