His father (Patrick) is rich, his little brother is named Dave, and their mother is never spoken of. He knows how to ride because he jumped when he was young, on horses that made his competitors cry, although he hated ever moment of it except those few spent in flight over barriers designed to fall down if touched.
He joins the Air Force because a) it means he won't ever wind up working under his father, and b) planes fly better than horses, although he occasionally misses the smell of hay and leather and horse sweat, the feel of a velvet nose pressed into his palm. (And c) there is, way back down deep, a part of him that needs to protect someone, something---he doesn't realize this until it's too late, though.)
He marries Nancy because everyone thinks he should, and she leaves him because she thought she was marrying the son of a wealthy father, not the soldier he becomes.
When he arrives in Atlantis, it feels like home, but he doesn't know why, or what it is that draws him so strongly to Chaya.
2. several steps to the right
His father (Rob) is USAF, just as John will be, and would spend his life in the air if not for his wife Ana, who is an orphan and generically foreign and just a bit strange---but beautiful and impossible not to love. She and John both sleep scarcely at all and spend the gray mornings telling stories to each other. When she dies, her husband breaks more than just a little; no matter how he tries to put the pieces back together for the sake of his only son, the cracks just gape wider every year. He winds up with early-onset Alzheimer's, and John spends the last two years of high school living with his grandparents, who own a farm (and a bad-tempered horse).
He joins the Air Force because he is very much his father's son, and there is nothing else he could have done and remained himself. His wife, Deb, comes from a very wealthy family and fell in love with him partly because he doesn't. And she leaves him because she cannot understand why he would rather have his feet in the air than on the ground with her. (In between, her father teaches John how to play golf---other than Deb, it's the only thing they have in common.)
Atlantis is home in the way his grandparents' farm almost was, and he knows exactly why. And when Helia and her ship of time-refugees show up, he refuses to simply hand over the keys and walk away.
(And if, perhaps, he found himself reliving that first, desperate year, he would tear himself to pieces in the attempt to make things go right.)
3. several steps to the right + magic and tattoos
There's magic and John can see the shape of any man-made thing's past, although he locks away that part of him so that he can fly. Deb gives him wings so that he can't fall, and then hates him for using them. Sometimes his shadow talks to him, sometimes it doesn't, but Atlantis is always the most beautiful thing he's ever seen. She works her way into his head, his bones, his heart.
He's still a soldier, would still choose the people in her over the city herself, if needs must, but he might never recover from making that sacrifice.
In this world, he manages to save Sumner, to turn Michael into an asset, a friend. He makes other mistakes, but not those.
(And if, perhaps, he found himself in a different world, where he had been a different man, he would give up anything to go home again.)
4. one more step to the right, no magic this time
John's father is in an accident---non-fatal, but career-ending---and so John spends his childhood on his grandparent's farm instead of on Air Force bases; his mother is very ill at one point, but recovers. When John goes to college, he majors in mathematics but plans on becoming a farmer. His roommate turns out to be a spazzy genius kid who's studying physics.
Deb never enters the picture: there's Lucy, instead, who suits him in all the ways Deb didn't, and is thrilled when he starts a sideline crop-dusting business.
Atlantis . . . well. I did mention that John's mother is still alive, didn't I?
Well. There are a whole bunch of possibilities, just nothing I've written much of yet. There's the John that grows up in the Roman Empire, the John whose father lost everything when some financial bubble burst, the John who's entirely Alteran, not just mostly, etc.
Every now and then I read back through all the bits and pieces scattered through my notebooks and feel this odd mix of elation and despair.