Complex sentence: In other words, he appears to have fostered artistic grandchildren, despite having no direct disciples outside of Parma, where he was influential on the work of Giovanni Maria Francesco Rondani, Parmigianino, and Giorgio Gandini del Grano.
Split into simpler sentences: In other words, he appears to have fostered artistic grandchildren, despite being barren of direct disciples outside of Parma. In Parma, he was highly influential on the work of Giovanni Maria Francesco Rondani, Parmigianino, and Giorgio Gandini del Grano.