Many fans really don't want to let the original trilogy go, despite it most likely being for the best as we could do away with any character-based ties and focus on the mythology of the world itself. Anyway, a popular theory is simply that your new character is Shepard's child, conceived before the final battle for Earth, and no matter which ending was chosen (although Synthesis certainly throws up some questions) you were quickly stashed away and made your way to the Andromeda galaxy... at some point... somehow. I mean, sure, okay, maybe. For this to even begin to be plausible, you'd have to factor it into the one of the aforementioned 'preparations to leave Earth were underway'-type theories. It's definitely plausible for a wild billionaire or the ARKCON faction to gather up a newborn child as they depart for Andromeda - the purpose being to guarantee as long a life as possible once they arrive - but by itself, this feels more like people desperately hoping for something that guarantees Andromeda feels like a bigger part of the canon. There's also the fact that if you played a lone wolf or had homosexual relations, this entire thing would have to be some sort of 'adopted child' angle? Yeah... it's not the most plausible. Back to the awesome stuff...
