Y'know how Sans and Papyrus never saw a human until Frisk came?

How the bunny vendor and most of everyone else said they just popped up one day and no one knew where?

Well what if

What if

Sans and Papyrus are younger than they appear?

Dating back to Chapter 25 I stated two theories:

That Sans and Papyrus could be Gaster's sons

Or

The manifestation of his split soul after a collision with a human one (somefuckinghow, I'm gonna tackle that one later)

And I'm going to use those same two theories to shed some light on this matter.

Let's start with the Family theory.

Let's say Gaster had a baby mama, married her (or not) and had the skelebros but they were too young to really remember her. The war broke out and she got separated or killed and Gaster had to raise the boys on his own in Underground while still juggling his job as the Royal Scientist. After the sixth human came (Sans could be about seven or so and Papyrus still a youngling) he had the mishap in the lab and fell into the CORE, thus erasing his existence.

Though I'm not entirely sure how him being erased doesn't affect the bros' existence since he is their father, they should be erased as well if you think all Doctor Who like.

But anywhore!

Sans and Papyrus lived on their own for a few years, Sans obviously the responsible one and making sure Papyrus ate and was healthy, both of them not remembering how they got there or who their parents were, until Papyrus got old enough to do things by himself, like 'cooking' and wanting to like the Royal Guard. And seeing Papyrus do things by himself gave Sans that sense of pride that he did right and could now relax (a little too much if you ask me).

If they really came after the sixth human then there must be a major time gap between then and when Frisk fell, thus explaining why they've never seen a human before. Especially Papyrus since he such 'human hunting FANATIC' and doesn't even know what a human looks like.

Sans could be in the same boat as Papyrus but to me this in only plausible if there was no reset, because technically he recognizes you after the first and so on.

Now on to the other theory.

Imagine Gaster having no baby mama, never got married and the war happened. Six humans later the heifer falls into his own creation, he's ripped through time and space, his own soul collides with an unknown human soul and banished him to the void. Where he's alive but dead at the same time, here and not here, between the (code) lines quite literally. And then his split souls created Sans and Papyrus, possibly at the body size they are now, but it has to be after the sixth human since again they don't know what a human looks like, or they don't share the same memories as Gaster. If they were created at that body size then they could be rather young, but know what an adult would because of the knowledge Gaster had. By default.

Not sure if you agree with what I said but I felt like writing this XD