Sounds like a cat, to me. ;)

They're all different. My mom has a cat that no one ever sees. It's like she lives with a ghost. Apparently, when she goes to bed, the cat is all over her for attention, but I don't think any guests have ever even seen the cat. I'd think my mom had invented the cat if I hadn't been the one to bring her home as a foster kitten years ago, lol. Her littermate brother (raised in the same house and still lives there) is in everyone's face all the time, so he doesn't seem to be afflicted with whatever flakey personality traits his sister has.

One of mine is the sweetest cat ever. She really doesn't have a mean bone in her body. I can't imagine this cat ever attempting to defend herself from a person. My other cat is very affectionate, but also very opinionated. She'll bite someone at the drop of a hat.

They're all different. Your friend just has a cat that leans more toward the aloof side. Not a big deal.

I agree with JenC. Sounds like you each have a cat! Personalities are something you don't see fully in cats until they are comfortable in their new homes.

Unless you see some physical changes (weight loss, lethargic, drooling, drinking excessively) there is no reason to worry; this is assuming both cats have been neutered and have all their shots and vet exams. If not, there is your start.

I would put a lot of time into giving that kitten personal attention by playing with it gently (get toys on strings, beanie babies, etc). If the cat does not want to be held, do not hold it, but create a relationship with it now, while it is still young.

That's one of the huge benefits of being owned by a cat - no one cat is ever just like another. My last cat was a lap kitty; current cat would rather attack your ankles and run laps around the house than be held (although I have been able to hold her briefly just before she goes to take a nap).
Enjoy your kittens!

Also, as your cat gets older (I mean more than 1 year, maybe 2), he'll settle down, and may become more affectionate and cuddly. It sounds to me like your kitten is restless, has excess energy, needs an outlet, and needs a companion to run with. If I were you I would get another kitten for him to live with. Note that if you get him a companion kitten, there may be a few weeks of adjustment, but then I am certain you will have a happier, calmer, more affectionate cat.

It could be that the kitten is still in need of socialization. If he wasn't handled by humans during the "critical" time frame, he might just need more time to become socialized. Our Shizu was very shy when we got her. She purred a ton when she was petted if she was lying down, but when she was on all fours, she'd run away when approached. This went on for awhile. Eventually (with much patience on our part) she became the mommy's girl she is now.

Also, I've seen a number of kittens at the shelter (where I volunteer), would still run away or squirm while being held (after they'd finally gotten over the hissy phase), turn into the biggest mushes through the attention (socialization) of volunteers and staff.

It might turn out that this particular kitten is "wired" to behave like he is (our Miku is a strange little cat!), or it could just be that he needs more time, and attention. There's a lot of info on how to socialize kittens out there, perhaps you could give it a try.