There seems to be a general consensus (unless I'm just not looking in the right places) that John Sheppard is rebellious son of Old Money. And I can see that, and I can even believe that the writers intended this. But I seem to have gotten a different impression.
I think John's the rebellious son of New Money. I think he's closer, in that regard, to Lex Luthor of Smallville than Jim Ellison of The Sentinel.
And I'm basing this on relatively flimsy evidence, too. :)
1. The newspaper clipping called Patrick (note the name) Sheppard a utilities mogul. Now, "mogul" does mean wealthy, powerful person, but colloquially (or at least to me), "mogul" implies self-made. You don't call the son of the big publisher a "mogul" even if he's running his mom's empire. You reserve that for the person who built the empire.
Now it could very easily refer to someone who used inherited money to make their own place in the world, but such a person would not insulted if their sons also went their own way. But a man who started from scratch might well think his sons have a duty to continue this.
2. Sheppard is an Irish name. It's also English, but the Patrick is suspicious. There is Irish Old Money, of course, but most of it is only a few generations old - the Kennedy wealth comes from Joe Kennedy, JFK's father.
3. I know so little of general funeral customs - that wake with the closed casket in his own house - is that typical of any group?
So, this is the back story I'm creating in my head:
Patrick was born just at the tail end of the Depression in 1939. He's family is maybe a step above working class. He's smart - brilliant, in fact, ambitious and athletic - enough to get a scholarship to Harvard in 1957 (which is nicely between Korea and Vietnam, and so if there is a draft, he'd get deferred immediately.) And being charming and bright, and maybe better socialized than his son, he makes Old Money friends and decides he wants that life - all the trappings of it - multiple houses, horses, children who follow his legacy, all of it. Maybe he even marries a friend's sister after grad school. If he has a kid right away, he's permanently free from the draft. Twenty years earlier, he'd have become Episcopalian, but by the time he finished college, JFK is president and it's okay to be Catholic, although his wife doesn't convert.
And he gets it. He becomes wealthy and powerful and can act just like his college friends, and he raises his sons to be like Old Money. And David is perfect. He likes that life. He happily follows Dad to Harvard and now he's a director in Dad's company, and he'll take over now.
But John? John's a rebel. He doesn't care about the money. He likes the horses, but he likes skateboards and surfboards and ferris wheels, too. See, if Dad really was old money, John's going to Stanford (if he went) would have been easily explained. "John's very much interested in computer science, and much as it pains me, Stanford's program is better than Harvard's." But Dad sees it as a rejection - "Thanks to me, you're a legacy! How can you turn that down?"
And he does want to fly, but he also joins the Air Force because Dad offered him a job in his company - I'm assuming John was a math or engineering major, or even computer science - and John turned him down. Didn't want to come back East, didn't want to be under Dad's thumb - who knows? Wanted to make his own way. And Dad cut him off from any allowance. So John joins the Air Force and goes to pilot school, and he's reasonably happy.
He meets Nancy, and Dad likes Nancy. There's hope of a real reconciliation when they get married. But he's doing whatever he's doing in the Air Force and then something else happens - I have my suspicions, but there's nothing to really prove it (other than David's reaction to Ronon.) And the marriage fails, and with it any real hope for John and Dad.
That's my back story, anyway.