Unusually he doesn't seem to "do" milk. Most cats I've known have been big enthusiasts of milk. Since they all tend to like fatty stuff (fat off of meat, butter, margarine, cream, cheese), I'm surprised that he doesn't touch it.
I've tried a couple of times, once when he first arrived, and again yesterday, in case his initial disdain was a function of stress.
I wonder if he doesn't really know what it is? I guess it's relatively low smell, compared to the cat food (and even the dry stuff I've given him, has a quite strong meaty smell), and if he's not had any milk since he was a kitten, and even that would have been directly "on tap", so to speak, he may not realise what it is.
I wonder if seeing the kitten drink it will stimulate his curiousity? Quite likely when I introduce them, it'll be over a meal, since that tends to overcome any risk of fighting, in favour of stuffing their faces!