Excerpts from Books and Wikipedia
"Cleisthenes (...) was an ancient Athenian lawgiver credited with reforming the constitution of ancient Athens and setting it on a democratic footing in 508 BCE. For these accomplishments, historians refer to him as "the father of Athenian democracy." He was a member of the aristocratic Alcmaeonid clan. He was the younger son of Megacles and Aragiste making him the maternal grandson of the tyrant Cleisthenes of Sicyon. He was also credited with increasing the power of the Athenian citizens' assembly and for reducing the power of the nobility over Athenian politics." [Wikipedia]