This article has loads of spoilers in it. Really specific ones, too. Proper end game ruining stuff. You've been warned.
There's no denying that Uncharted 4 is a game created in a post-The Last of Us World. Rather than being a middle-of-the-road jungle caper, Uncharted 4 is a surprisingly (for the series, at least) rich text that explores many things that I could spin into separate articles: the differences between treasure and wealth; every one of the applications for 'A Thief's End'; thematic similarities between Uncharted 4 and beloved Sean Astin biopic The Goonies. But the most interesting bit of all is how directors Neil Druckmann and Bruce Straley, and the writing team lead by Druckmann and Josh Scherr - and, by extension, the game - treat Nathan Drake himself.
Up until now Nate has been a charming, quick-witted adventurer in the same mold as Indiana Jones, but without the boss hat or undiluted sexual allure of early 80s Harrison Ford. The only lasting relationships Nate had were with Sully and Elena, gruff father figure and love interest respectively, but these were never examined in any detail. Some mild tension was introduced by Elena and Nate continually breaking up and getting back together, but we weren't given reasons for this beyond Elena preferring her boyfriend/husband to not deliberately walk into situations he knows are likely to kill him, which isn't an unreasonable request when you think about it. But Uncharted 4 gives our hero not only an older, craggier face, but a complex personality of his own, and it boils down to this:
Nathan Drake is a pretty fucked up dude.
I'm not making this up; it's established very early on. Chapter 3 is deliberately set up to make you think Nate Drake is all business as usual. By titling it 'The Malaysian Job' and starting mid-scuba dive, the player thinks: "Aha, Nathan Drake and I are going to steal indigenous Malaysian artefacts!" Nate hand waves away concern that he's running low on oxygen; there's even a bit where the shipping container he's retrieving groans, and you assume it's going to fall on him because that's what would happen in an Uncharted game... and then it doesn't! Uncharted 4 actually plays with its own tropes! When it turns out Nate is working a normal job for a salvage company you realise he didn't want a fresh oxygen tank because he needs to feel some kind of thrill, some kind of danger, even if he has to introduce it into his life artificially - he ought to be careful; that's what did for David Carradine. Without having to directly explain anything the writing and direction in this short sequence make it apparent that a) Nate has settled into some kind of domestic drudgery and b) he's not coping well.
While you'd think this would be the main reason Nate and Elena's marriage has issues, it's not. It's not that he goes adventuring, it's that she comes second to it: when Nate is describing his life to Sam, he forgets to mention he and Elena are married until after he's mentioned all the other stuff, and if you're in a relationship you'd hope your partner would move you up front in the 'significant events of my life' stakes, even if other events include occasional zombies. The game has this dynamic woven through it, and uses it as a lens to get a focus on Nate. It's no accident that, of the 36 optional conversations to find in Uncharted 4, 11 of them are with Elena, and for most of those she and Nate talk around their relationship problems.
It's also significant that these conversations happen after chapter 16, a flashback of young Sam and Nate sneaking into a manor to find their mother's possessions. In the process they discover letters cataloguing the breakdown of a family due to one member pursuing treasure and adventure instead of maintaining relationships - a person who lives alone in a house of dusty monuments to past glories, and coughs herself to death whilst wearing a black turtleneck like a shit mime. The placement of this chapter is incredibly well timed in the story, because we've already seen Nate withdrawing from Elena to spend time in his attic of mementos, and this reinforces what's really at stake for them other than pirate treasure. By reintroducing Elena at this point in the proceedings it's not just returning to the partnership which established their relationship in the very first game, but giving them a second crack at it with the benefit of maturity and hindsight. The sour note is that the devs couldn't think of a way to crowbar Elena in that didn't involve her happening to be near the bottom of the cliff her husband fell from (although given how much Nate's survival classically relies on luck rather than judgement we could probably write an essay on that too).
When Nate first lies to Elena about where he is it's not a surprise to the player: it's set up in the previous games that she doesn't like it when he knowingly walks into danger, and we've seen in various flashbacks that sneaking off has been a go-to tactic of his since childhood. What's more interesting, though, is that he never told Elena he had a brother.
The sheer scale of the 'I've always secretly had a brother' retcon that Naughty Dog shoved into this game is staggering not just in the context of four other games, but especially when taking into account all the tie-in comics and novels, all of which are absent the mention of one (1) bonus Drake with a neck tattoo. But Uncharted 4 gets away with the sudden appearance of Sam because it's tied in to Nate being emotionally broken. It would have been incredibly easy for the writers to give Elena a hackneyed line of expositional dialogue, like: "Sam? Your older brother who died in a Panamanian prison 15 years ago?" But they didn't. They're now making it canon that Nate had never, ever, mentioned his brother. That, let's reaffirm, is fucked up.
I'm not making that judgement without sympathy. Nate is a man whose mother may well have committed suicide, whose father abandoned him, who was tossed into a Catholic orphanage and went unmissed when he ran away. It makes complete sense that he has issues with abandonment and doesn't like being emotionally vulnerable. Nate's probably been waiting for Elena to leave him the entire time. Even Sam left him. By being shot, sure, but left him all the same.
This is the other defining relationship for Nate: the one he has with Sam, and you can see how it changes between the Drake boys as children versus adults. As a teenager Sam was able to take the lead, but as an adult he's outpaced by Nate: Sam's animations show him catching handholds a little lower down, climbing more slowly, and swinging with less precision than his brother. At the start of the adventure he's making fun of Nate's skills with a rope; by the end he's commenting out loud on the jumping feats he has to follow. But the differences are more than physical, even though Nate's lush, un-receded hairline is probably a key source of resentment for Sam.
Whilst Nate has been maturing and discovering more lost cities than there is reasonably room for in the world, Sam has been sat in prison for 15 years, stewing over the same pirate treasure they were after in their 20s. When Sam asks "How long we been chasing this thing, huh?" he doesn't realise that for as long as he has, Nate hasn't. It's why Nate has to flat out tell him that they're "not those kids anymore," which must sting given the knowledge that 'Nathan Drake' was Sam's creation all along, stemming from when he suggested the brothers change their name and go looking for Francis Drake's treasure. In the intervening years Nate was able to grow on his own, so now Nathan Drake has become more realised without Sam than with him, and despite the fact they've been trying to regain the dynamic they had in their youth, Sam has emotionally taken on the role of the younger brother, something which the voice actor Troy Baker has discussed. It's arrested development.
Sam is dealing with some lingering resentment and abandonment issues of his own because, knowingly or not, Nate left him in a prison for a decade and a half, but he's also a mirror giving Nate perspective on what a selfish, reckless, absolute pain in the dick he used to be. Near the end of the game Nate grumbles that Sam's behaviour is ungrateful given what everyone else has sacrificed to save him, which is a role reversal for literally every other game in the Uncharted franchise. In Uncharted 4 Nate is essentially going on an adventure with his younger self: by looking at Sam he understands his own behaviour, and how damaging it can be. Without Sam there would be no Nathan Drake in the first place, or in the last place.
The details about Nate's past, and the emotional complexity he's been given, not only add depth to Uncharted 4, but also a (very thin) retroactive layer to the old games. Given the new context we now know not only that Uncharted: Drake's Fortune, the first game, takes place around five years after Nate had lost the only real family he had, even if he is very jaunty about the whole thing.
Nate Drake's image change from a wisecracking rogue with a wink in his eye, a gun in his hand, and an illegally obtained artefact in his back pocket, into a sad, deeply flawed man whose constant jokes are almost definitely a defense mechanism may not be welcomed by everyone, but dammit, it should be. It doesn't take away the ridiculous set pieces, the explosions, or the trail of bodies left in Nate's wake; on the contrary, it makes them all make sense! Naughty Dog has effectively disarmed the jokes that a man that enjoys that much danger and kills that many people must be be fucked up by going: "Yup, he was fucked up the entire time." Well played.