Where did the Sada/Turo Are Married theory come from? And is it true?

I've heard this theory floating around that Professor Sada & Professor Turo exist in both versions, are married, and are Arven's parents, with the opposite professor walking out in his childhood depending on what version you play.

Now this sounds like an interesting concept, but having not played the games myself yet, I can't confirm one way or the other. Is this confirmed explicitly in the actual games, like in a cutscene or something, or is this just like a headcanon that serves as interesting fanfiction material? (I like the idea to be clear, but am unsure if it's factual)