Nathaniel knows when Anders' smiles are genuine.
It is not something he learns immediately, for Anders is quick to crack a joke and smile at just about anything. It is ridiculous to hear but Nathaniel keeps silent for much of it at first, because he knows much can be learned by what a man doesn't say.
The commander insists that both Nathaniel and Anders are with him on every mission. Nathaniel doesn't understand mages, and asks questions. Anders deflects the questions sent his way. After awhile, Nathaniel stops trying to understand mages and starts trying to understand Anders.
He sees the first glimmer of a smile that's different when Anders is talking with Oghren. They are talking about alcohol, with is not a suprirse, and then Oghren laughs at something Anders has said. And in a flash, there is something different in his smile. Nathaniel notices it in Anders' eyes.
These brief moments start to occur in greater frequency, but it is when the commander gives Anders a small kitten that everything changes. Anders face lights up at the sight of the animal - a little too thin and need of some tender loving care - and the kitten meows when Anders picks him up. This smile is completely different than all the rest.
The story of Mister Wiggums is not one Anders has told Nathaniel when talking about the Circle Tower, and it is not one Nathaniel will soon forget.
Ser Pounce-a-lot is given free reign of the Keep, and is not always by Anders' side. But when he catches up to his human, Anders has that same bright smile. It is completely genuine.
There are times when Nathaniel goes to seek Anders out, for any number of reasons, and he notices Pounce bat the fabric of the mage robes, or try to knaw on the boot. Anders laughs and picks him up, kissing the kitten on the top of his head.
The task at hand can wait a moment, and Nathaniel watches from the shadows until Pounce squirms in Anders' arms to be let down.
Anders knows when Nathaniel is watching.
If they were not Wardens, then perhaps he would not. Nathaniel is accomplished in his skills with stealth and subturfuge, and it is only the pull of the Taint at the back of his mind that alerts him to the presence of another. At first it had been disconcerting, since it was similar to the pull of darkspawn, but now it was a comfort of sorts.
He knows it's Nathaniel because he does not interrupt at first, when Ser Pounce-a-lot is true to his name and pounces on his boots. Anders knows the kitten is hoping to catch Anders without those boots, to catch a wiggling toe and then lick it with his scratchy tongue. Nathaniel waits.
It is not something he expects of the rogue. Nathaniel comes off to him as a dog person, and is fond of the commander's mabari. Nathaniel is very much about getting a job done. So when he waits, it makes Anders wonder.
But it is hard to wonder for long when Pounce rubs his head against his chin.
Nathaniel always waits until Pounce has had his fun and is on his way again - a kitten on a mission - before he approaches Anders. He pretends that he saw nothing.
He does not always understand Nathaniel, but when he waits so patiently, it makes Anders want to.