How similar does a character's backstory have to be to their canon one?

For the character I'm looking at, his backstory revolves around an Oddly Specific Prophecy that results in him being adopted by a wealthy couple and basically wanting for nothing his whole childhood. But since there's no prophecy here, would it be ok to have his Recolle counterpart still living with his birth parents, for instance? (Character is Ivan from Golden Sun, btw.)