"He was very real, Yuna. Both in Zanarkand and in your Spira."

Auron has a theory about this: the reason the Fayth were able to dream both Jecht and Tidus into the future was because they'd been famous blitzballers, and enough of the Fayth remembered them to reconstruct their memories. It's only a theory, but he assumes that's why Spira ended up with two blitzball stars and not simply some random person.

"And yes. The Farplane..." He pauses, and his voice is thick when he continues. "It exists, and the sent exist there too. They're waiting for us in the light."