Sometimes Bones thinks that they both know, and that the whole thing is one big prolonged joke. One day he'll fall for it, open his big mouth and ask, and Jim will shout “Got you!” and Spock will smirk as much as he ever does while Jim falls against him, laughing. “Of course we know,” Jim will say. “How could we not?”
Yes, because Bones finds it so absurd to even imagine that they could not know. He watches as they stand too close and lean in too close and panic for each other over nothing. He watches them watch each other over chess games, in the rec room, on the bridge, in Sickbay – hello, Jim, eyes over here!
Sometimes it's – and he'll never tell anyone this, don't breathe a word of it – sweet. Sometimes it's frightening. Because surely they know. And if they don't . . .?
Sometimes he is sure that Jim knows. Speaking to Spock, Jim drops his voice to a low lilt, grins that warm grin that means he's flirting. Jim could dance the mating dance with his eyes closed or with his hands tied behind his back – he often does. Jim knows the nuances words have, how they carry emotion, in ways Spock can't understand. Surely Jim knows, if either of them know.
Bones has seen Jim talking his way into some gorgeous thing's bed, when Spock will appear, uncomfortable and out of place in the bar. “A situation has arisen, Captain,” Spock will say and of course Jim is a good captain, he stands, he says “Be back soon.” They leave together and of course it isn't a big deal. Only a few short minutes and the not-really-a-crisis is over and Jim is free. But instead of turning round and heading straight back to that bar, Jim will turn to Spock with this sly look, saying “Spock, my friend, I think you deserve a night out.” Spock will protest that Vulcans do not require as much rest as humans, that it is illogical to expend energy for the purpose of resting, that no, Captain, Vulcans do not need recreation. “Nonsense!” says Jim. “That's an order!” says Jim, his eyes mischievous but not malicious, no, behind the teasing is a happiness burning oh so bright. The next day when the crew gets together to share tales of their conquests, Jim leans back in his chair, smiling like he has something better, his eyes staying fixed on Spock.
Or maybe Jim is too darn oblivious for his own good. Jim, who ignored an onset of Uthyrian flea because he was busy being a captain, who ignores everything when he's too busy being a captain. Maybe it's Spock who knows. Spock likes to act naive, and sometime he honestly is, but Bones has heard him understand idioms and later pretend they confuse him. Spock puts on this act where he doesn't know what Jim gets up to when he goes off on Shore Leave, when the truth is Spock keeps tabs on everyone Jim takes to his bed. Spock probably has a more thorough list than Bones, which is saying something since Bones is the one forced to listen to Jim's rambling tales the morning after, though if asked Spock would probably say his actions are to ensure the safety of the ship. In a pig's eye!
Now that he thinks about it, Spock has this curious habit of interrupting Jim in the midst of a seduction with some pointless paper work Jim has to sign or some other triviality. Bones has watched the scene play out many time – Spock enters, hands clasped behind his back, pointedly not raising an eyebrow at Jim's proximity to his lady friend. Jim's look is often startled, than sheepish. He then begins to act extra official because “Bones, how can Spock respect a Captain who's too busy flirting to do his duty?” The two go off and be Starfleet officers together, and Bones doesn't think he imagines the smug expression that threatens Spock's impersonation of granite when Jim hangs back to play chess with him, and the lady friend flounces off into the night.
No, Bones is pretty sure Spock has a fair idea of just how much he means to the captain. That's the best reason Bones can give as to why he's always pressuring the Vulcan about his friendship for Jim, needling him with insults, accusing him of not caring. Spock knows Jim cares and Spock cares back and Bones knows Spock knows, so why hide it? But then Jim will wander by Sick Bay and say “I think you hurt the feelings he doesn't have again.” That's when Bones wonders if he has it all wrong, if Spock doesn't get it and Jim doesn't get it either.
There are so many moments he's thought: yes, this is it. This time they'll see it and stop hiding it. When the virus struck and Jim hit Spock and Spock threw Jim and then they pulled together and saved the day. When Jim was split in two and Spock helped him through it and didn't even think to take the captaincy, not once. When Spock betrayed Jim to protect him and Jim forgave him. When Jim was framed and Spock spoke for him in a way that defied Vulcan impartiality, challenged a computer for Jim. When Spock killed Jim except he didn't – isn't tri-oxide a useful excuse? – and wanted to die when Jim was dead and smiled enough to split his face when he found Jim alive. Moments and moments of rescues and confessions and closeness.
Bones knows why he says nothing. Whatever the two have now, whether they care to recognize it or not, or give it a name – it's right, it's healthy, it's working.
There's nothing that Bones can prescribe.