Feral behavior questions

I'm fairly new to this feral care thing, so I have a quick question.

I am looking after three kitties.  Two are probably siblings - an orange and white boy we call Brighton, and a grey tabby we named Esther.  They are most likely less than a year old.  Both have been fixed, ear tipped, and given shots.

Brighton and Esther both have shown signs of increasing tolerance for human proximity.  But Brighton has become...interesting.

We feed the cats on a patio, next to which is our deck.  If I put out a bowl for Brighton and he finishes it, he'll hop onto the steps and hang out for a bit.  I typically add some food for him, as that's often a sign he's still hungry, but even after eating his fill, leaving food in the dish, Brighton hangs around us.  He'll lounge no less than 5 feet from us at times, bathing and looking utterly content.  

He's even making soft-eyed looks at us, indicating relaxation, pleasure, and happiness at seeing us.  Yet is IS feral - this kitty utters no sound whatsoever and will NOT permit human contact.

What do we make of this?

Cats are individuals.  Some ferales may get almost spontaneously socialized - esp if kittens - while for some it takes years...   And yet they can be from the same litter.

compare the behavior here in this case with home cats.  not all cats are lap cats. yet the same cat who is no lap cat, likes to be around its owner, laying perhaps somewhere near a couple of meters, and uttering friendly noises - for example the younger of my residents.

of course, our resident, being also a home cat, do like normal petting too.  

Good luck!

Stephan is right - cat's are so individualistic, what works for one will scare another in the same litter. I would sit and talk softly to Brighton (maybe read out loud to him). If he approaches, offer your fist, fingers down, for him to smell. It will resemble a cat's head, for a head butting greeting. Don't attempt to touch him unless he clearly is open to it.

He may come around with patience. Good luck!

Thanks.  So far, he keeps his distance, but seems to want to hang around the back of the house, especially if we're out there.  It's rather endearing.  We'll see how he does with socialization.