Who knows .. maybe its Arceus;-) (lol). But i don't beleive its Silver, because of the fact that Silver of the Adventures Manga is some four years younger than Red (whom Ash is based upon).
Well, I was watching 'Lucario and the Mystery of Mew' recently, and an idea sprung in my head. I've never read it around here, but I think it's relatively obvious.
Now, we know who Sir Aaron is, right? Sir Aaron is an 'Aura Master', depicted as a hero in a small town near the Tree of Beginning where the movie takes place. Aaron is skilled in controlling Aura through his gloves, though whether the gloves are necessary for it's channeling is unknown.
The movie makes it very clear that Ash and Aaron are connected, whether through blood or otherwise is not certain, but genetics seems to be the most immediate assumption.
Ash and Aaron are connected in the sense that they both give off an identical Aura Pattern. Aura is the essence of life, as some put it, and each individual has his or her own Aura pattern. We know that Ash's and Aaron's are identical because Lucario initially mistakes Ash for Aaron through his Aura sensory and not his eyes.
Also, Ash is able to help save the Tree of Life in the end because he possesses the same Aura patterns as Aaron, which he amplified through Aaron's gloves. So, maybe its him? Any idea?