Does the godfather of my child have to be a catholic?

I converted to Catholicism two years ago. My brother, who my wife and I would like to be godfather to our first child is not a catholic. My sister and law, who we would like to be godmother, is a catholic. So my question: does my brother need to be a catholic in order be godfather. Not "should he be" etc. . . but is it "required"?