Simplify the following text for a Grade 9 native English-speaking person.
Original: The traditional account of Roman history , which has come down to us through Livy , Plutarch , Dionysius of Halicarnassus and others , is that in Rome 's first centuries , it was ruled by a succession of seven kings .
Simplified: The traditional account of Roman history is that in Rome 's first centuries , it was ruled by a succession of seven kings .