I am looking at this photo and I think the depth of field is a little shallow. You captured the cat and the front of the arm very sharp and in focus, however, the face is slightly out of focus. I experience this all the time with my 50mm f1.8 lens. I have since consulted the Online Depth of FIeld Calculator and learned some things... Using f2.2 with a focal length of 50mm at a distance of 3 feet on a 1.6x sensor you get an effective range of focus of about 1 inch.
Just fixing that one minor issue would make this photo a perfect ten!!
I like this image but I see some points that can be improved. It looks to me like the focus is more on his near arm than his face. The background is also a few stops too hot--it's bleeding onto the boy, blowing out the highlights on his shirt and arms and creating a strange glow around his head. The boys pose looks relaxed, but his expression looks more sad or pained than loving or protecting. I also might put a reflector or bounce card camera right to give a nice catchlight in his eyes and provide a bit of directional light on his face.