I would still say kella because he wrote for other people as well.
R Kelly wrote for changing faces, Aaliyah, Charlie Wilson, b2k, rue en studdard, Trisha yearwood, Celine Dion, kci and JoJo, nivea, puffy, usher, Micheal Jackson, Ronald Isley.
Once you know a song writer like R Kelly and Babyface you can instantly tell the songs they write because they typically produce them so they are phrased in a very noticeable way.
R Kelly simply has more solo hits than songs he sold to others
Both brothers are extremely talents.