I've got two kittens. A boy and a girl. I've had them for both a good couple of months now. The boy has lately started to hide from me, well not only from me, from my boyfriend too. He wasn't like this before, he used to be so friendly now all of a sudden he just does not want anything to do with us.
Sometimes when the girl sits on my lap and she's purring, he'll slowly come out from where he was hiding and jump up next to me. But most of the time, he'll just hide.
When I come home from work, he'll be sitting on the sofa, but as soon as he sees me he'll run away as fast as he can!! When he's eating his dinner and I'm just about to walk past him, he'll run!

Is it time for him to get spayed? Is that what it could be? He's around 6 months old.

First thing: If they're around six months then you want to get them both fixed (otherwise they will mate with each other).

As for the hiding: Can you think of anything that's happened that might have led him to be frightened? It could be something as simple as your body language, something he sees in it that he finds intimidating or scary (you may not be at all aware of it). THey're such keen observers. I went through this with one of my cats: I came to realize that sometimes I speak in a voice that, for some reason, just really scares him. My only real suggestion is patience and trial and error. Make a sustained attempt to reach out to him, to show him that you're trying--they do resond to that, but it takes time. It's quite possible you'll never know what started him down this path, but you can definitely help him to find his way back. Try talking to him in different voices, moving slowly and softly when you approach him, that kind of stuff. (I realize you most likely have already thought of this, in which case just be really patient and keep trying.)

He'll come around in time. And neutering him should help, because he'll be a lot calmer.

Good luck to you both!