My cat is a year old and is the size of an eight week old kitten..

So, I have this cat name Gabriel, or Tiny Tim. We got him about a year ago, his back leg is shorter than the other, and his tail is curled like a monkey's. He's always sick, and has a regular diet, he's also getting medicine for his sickness, but he isn't growing. He's supposed to be around a year old, but he's very small. He still poops like a normal full grown cat, but he looks like a kitten. Does anyone know what could be wrong? I have over thirty cats around my home and have never once seen something like this

There are some cats that are like drawfs in humans...they always stay small.  What medical condition does your cat have, and what does the Vet say about his lack of growth?  They might be related.