How & why was Charlemagne directly descended from a Roman aristocrat named Flavius Syragius?
and then he begat Saint Arnulf of Metz, who was a bishop?
Arnulf gave distinguished service at the Austrasian court under Theudebert II. He distinguished himself both as a military commander and in the civil administration. Arnulf is the male-line grandfather of Pepin of Herstal, great-grandfather of Charles Martel and 3rd great-grandfather of Charlemagne.