Who is Moritz Levy from The Last of the Just and what is their importance?

Moritz is Ernie Levy's older brother. He is referred to as a pagan and a heathen because of his time spent carousing with the street gangs of Stillenstadt. Moritz is described as a realistic Jew...... hard-hearted and angry at the ways in which the Jews are treated. He frequently gets into fights.