Been playing FF7 for 30 years and I've honestly never really thought about this.
Outside of the brief mention of his parents, there is next to nothing mentioned in the game about Red XIII's origins.
It's never even said exactly what Red XIII even *is*. He's just a red, talking, cat/dog/wolf creature with a flame on his tail. Which is unusual in a lot of ways, even for FF.
There is mention of Red's parents (who are both gone/dead), and we get his father's name of Seto.. but nothing other than that. Red calls Bugenhagen his "grandpa", but that's clearly a term of affection and Bugen isn't literally his grandfather (unless there's some REAL weird stuff in the lore I don't know about...)
And of course, we do see Red with cubs many, many years in the future in a brief cutscene at the very end, which naturally begs the question: Where is Mrs. Red? And where has she been hiding this whole time?
I do believe Hojo mentions early on that both Red and Aerith are part of species that are going extinct, but again, there's no further information than that.
So. From a 30 year FF veteran to a community who might know some obscure lore or played an offshoot game I skipped:
What the hell is Red? Are there more of him anywhere? He clearly isn't the actual last one alive, but other than that, is he?
Edit: Redditors reading a post before commenting, challenge level: Impossible.
But also thank you to everyone who actually answered and let me know this was apparently addressed in a mobile game of all things. Which, no, I have not played.
Also yes I realize it has been 29 years. JFC the pedantry of Reddit I swear to god.