I believe Charlie Hume is in fact Charlie Pace.
And here is why...
When Desmond recently showed up at Hawking's church/underground lair, he inadvertently created a direct path from Ben to Penny. Ben promised to avenge his own daughter's death by killing Charles Widmore's daughter (Penny).
As the Oceanic 5 (minus Aaron) were preparing to return to the island via Ajira flight 316, Ben called Jack because he was 'sidetracked' after he'd visited an 'old friend' to tie up a 'loose end.' Penny was that loose end. Ben was bloodied and calling from a marina, where Desmond and Penny's boat was docked while in LA. Desmond tried to stop him, but Penny was killed and Desmond was injured in the process. Ben then took off on the flight. Desmond will try to find a way to return to the island in order to kill Ben. Leaving baby Charlie behind in Los Angeles...
Charles Widmore took baby Charlie when Desmond went after Ben (likely with Widmore's support and resources, now that they share a common enemy). Figuring that Desmond would never return, Charles took baby Charlie with him back to England. And even though baby Charlie was his only heir (that we know of), he put him up for adoption because a man of his age and in his position of power was not about to raise a small child on his own.
Simon and Megan Pace already had one son, Liam. But they were unable to have another, and looked to adopt. Simon was a butcher, and an associate of Charles Widmore (in the same capacity as Jill, the butcher in Los Angeles for Ben; storing bodies when necessary). Widmore arranged for the Pace family to adopt baby Charlie, and they raised him in Manchester, England.
When he was a young boy, Megan Pace referred to her son as 'special.' Daniel Faraday, whose research was being funded by Charles Widmore, told Desmond that he was 'uniquely and miraculously special." Like father, like son.
As for Desmond being Charlie's real father, consider their brief time together on the island. It seemed his main goal was to save Charlie's life...until it was out of his hands and the island had plans for Charlie's destiny.
- He used a golf club as a lightning rod to take the hit instead of Charlie's tent
- He rescued Claire in the ocean because he knew Charlie would have drowned trying to do so
- He saved a migrating bird for Claire because he knew Charlie would have died trying to do so
- He prevented Charlie from getting shot with one of Rousseau's arrow traps in the jungle
In the end, Charlie wound up briefly communicating with his mother Penny (unbeknownst to him) before sacrificing himself so that Desmond could warn the remaining survivors about the freighter and Claire would be rescued.
It is also fascinating that during Desmond's first flash back in time (right before he first met Ms. Hawking), he encountered Charlie outside of Widmore's office. Fate trumps coincidence in this instance.
In a Season 3 flashback, we saw Simon teaching young Charlie how to swim (and yes, I remember him claiming not to know how in S1, but that was because he was a drugged out wuss who didn't want to rescue the woman in the ocean at the time). I believe Charlie was destined to swim down to the Looking Glass to save his biological father and their friends on the island.
It is also not a coincidence that Jill worked at a butcher shop in Los Angeles that shares a name with Charlie's adoptive father (who happened to be a butcher). She works for Ben, but let's be honest...at this point it is still unclear whether or not Ben and Widmore used to work together or still are.
In addition, Charlie Pace's middle name (Hieronmyus) is an anagram for Hume's Irony. And Scottish philosopher David Hume was strongly influenced by another philosopher...John Locke.
So I suppose that in the pilot episode, Charlie Pace should have said, "guys, WHEN am I?" rather than "where are we?" If dad is uniquely special, it should follow that his son is also immune to the rules and effects of time...
Am I delusional; is at least some of this feasible?