Inquiry
Might Miguel be a person from Chrono Trigger?
Theories
Crono
Vaeran
Miguel is Crono, based on a few factors.
*Age. Crono was about 16 years old in 1000 A.D., and Chrono Cross takes place in 1020. Miguel is clearly middle-aged, so that works out.
*Appearance. Miguel has red hair and lots of it, though he wears it in a much tamer style than Crono did. He does not wear tribal clothes like the others of El Nido.
*Game mechanics. Miguel is ludicrously powerful, far more than a simple islander should be. In addition, he's an innate White. Crono could have been a Yellow in CC's system for all his lightning attacks, but his most famous technique was Luminaire, which in CC is a White element.
*Family. Leena looks a lot like what you'd expect Marle and Crono's daughter to; she's basically Marle with Crono's coloring. In addition, her name is very similar to Leene, a name from Marle's family. It's true that we see her "grandmother" and "sister" in Arni village, but they don't look a thing like her. After Miguel never returned from his voyage with Wazuki, an old woman in the village probably took Leena in as her own, as she no longer had any family.
*The scene in which you meet Miguel is also very telling. He seems to know a whole hell of a lot about the whole Lavos situation, for one thing. And if you watch carefully, the little Crono shade is always standing nearest him, and is standing directly over (behind) Miguel as he dies.
So what would Crono be doing all the way down in the El Nido archipelago, anyway? Remember that Porre invaded and conquered Guardia. We don't know exactly what happened to Marle, but it's pretty easy to guess: as then-queen of Guardia, she was either killed, taken prisoner, or is in hiding somewhere, possibly organizing a rebellion. Either way, not very pleasant. Knowing that things are going to get bad real soon, she entreats Crono to escape with their child. He gets as far away from Guardia as possible with Leena, settling down to a quiet life in a fishing village and changing his name. The only problem with this theory is that Crono uses a katana, and was powerful enough to defeat Lavos (let alone a boy from Arni).