So recently as I watched the 1954 version of Sherlock Holmes with Ronald Howard and H. Marion Crawford and was struck by the suddenness of something that was very...odd.
My ad lib of it is: Holmes: Oh, I just love tomatoes. I so love tomatoes!
Watson: *ignores*
Holmes: And I love them with cold lobster for breakfast.
Watson: *completely ignores*
Holmes: And I totally and completely love it for breakfast. Watson: *continues to ignore* Holmes: *whine* Are you still mad at me?
Watson: STILL? Yes!
Holmes: ...Why? I totally was--
Watson: You shot into our wall.
Holmes: ...it was patriotic (*yes, it was the V.R.*)
Watson: I DON'T CARE
Holmes: *pout* Fine, I solemnly swear I'll NEVER do it again. Totally promise.
Watson: ....really?
Holmes: *perks up* Are you no longer mad at me?
Watson: ...cold lobster and tomatoes? Really?
Holmes: ...yes? Please? No longer mad?
Watson: ... :-) nope. Let's eat!
Holmes: YAYZ!

And then, of course, there's House and Wilson, from House, M.D. Granted, it's already been said that House is pretty much a wounded doctor version (and due to me currently watching the episode with the "death cat", I am loving poor dark cat and all the superstition stuff).
I've noticed that despite House being a dick to everyone but in an equal way, which kinda helps I suppose, he is a little nicer to Wilson. When Wilson disappears or something bad happens to him, House goes out of his way to ensure he finds out what's wrong, as well as trying to be a mild constant in Wilson's life, even if it does involve them not being able to be roommates because House, unlike Holmes, is a bit of a child...

...okay, a very huge child.

On top of that, despite his equal-dickedness to everyone, he does care about Wilson and, to some extra extent, his team (who kinda work as Watson too) and is very child-like to everyone, not only to piss them off but also, in some ways, as help or to solve a problem.

But back to Wilson, who is House's Watson no matter what he does. Despite House's various attempts at being a dick, he does go out of his way to ensure Wilson is okay. In one recent episode, when Wilson had a chance to meet his brother, and despite having to solve a case and thus not meeting Wilson's brother. Still, at the end he did make sure that Wilson was fine, and agreed to join him in later.

I find it odd, though, that these two supposedly self-sustaining men need someone else, usually whom many accuse them of abusing verbally and mentally, to stay sane in some way, shape, or form. Holmes needs Watson because he 'asks the right questions' and because he is, perhaps, the first person who could not only room with him, but room with him for so long despite his eccentric nature and still want to (which probably explains why, after a while, Holmes finally just decided to drag Watson along on a mystery: if this didn't get him to leave, nothing would...except a really pretty client...). On top of that, Watson is one of the few if not only people who can call Holmes his friend, and Holmes probably doesn't know how to handle that but continually test the boundries of said friendship.

Sadly, the same thing goes for House: while Cuddy is a love-interest, she's more like Lestrade or another person in Scotland Yard, being there and influencing House but not as much as Wilson does. Wilson leaving during the first half of season 4 (season 5? I don't recall) threw House into a rut for a long time until he forced, in a way, Wilson to come back, as well as to realize that despite wanting to avoid House and his minorly self-destructive nature, Wilson had 'more fun' around House. Like Watson, Wilson sees this odd behavior as, in a way, excitement, and that is something that adds to the relationships.

If anything, the House/Wilson and Holmes/Watson relationship are very odd and seem destructive towards Wilson and Watson, but despite this, both House and Holmes go out of their way to ensure not too much takes place. True, Holmes is a little more clingy to Watson then House is to Wilson, but at the same time, they both do act like kids around them, and they both do worry more and more about their W's, if only because seeing them depressed can either put them out of sorts or make them boring (depending on which dick you want to deal with). Neither seem to enjoy being happy, as for Holmes he's only happy while on a case or with Watson in any setting, and with House the various times he is happy, he seems to screw up more then usual, which often causes him to turn back to his cranky-bastard mode (and in one case was even more self-destructive then usual).

Bottom line, I suppose, is that the H's of our equation are children and the W's are...somewhere between plush toys and security blankets, or at least a mild amount of parent. Both Watson and Wilson are the ones keeping Holmes and House in some form of sanity, and even when it doesn't work, they do what they can to ensure they'll be fine.

Oh, and then they have hot m/m sex.

...but only in slash fiction...