Complex sentence: Mosse was born in Berlin into one of Germany's richest Jewish families, where his maternal grandfather, Rudolf Mosse, was the founder of one of Germany's leading newspaper concerns and publisher of "Berliner Tageblatt".
Split into simpler sentences: Mosse was born in Berlin into one of Germany's richest Jewish families. His maternal grandfather, Rudolf Mosse, was the founder of one of Germany's leading newspaper concerns and publisher of "Berliner Tageblatt".