Why is my cat so strange?

One of my cats in a 12 year old boy and he's also a big baby. He was abandoned by his mother as a kitten and when he was found near death in an old farm house he was taken to a foster home where we got him (he was about 6 weeks). He is sooo needy, he is constantly kneading his paws on my bed like a little kitten, if he's ignored for just a short while he goes into a sulk and hides in a closet somewhere. A few years ago we didn't pay much attention to him for a couple of days (not intentionally) and he got so depressed that he stopped eating and couldn't even stand up properly, we thouh he was sick. As soon as we began loving him up he immediately got better. I love him to bits but sometimes it's just annoying when we have to go somewhere for a few days and can't take the cats, we worry that he's going to be miserable the entire time. Does anybody else have cats like this?