Jovoni I was the founder of JoJoLand and the great great great great great great great great great great great great grandfather of JoJo.
Jovoni XII was JoJo's father. He killed Jovoni I in attempt to take over JoJoLand. Jovoni XII actually loved Jovoni I's idea of making a land, but the XII was stubborn and wanted to rule JoJoLand. Many view him as a dictator. His life was ended by natural causes.
JoJo is actually the thirteenth generation of Jovonis. However, JoJo didn't like the nave Jovoni and wanted to be different. This caused him to rename himself as JoJo. JoJo is the current mayor of JoJotown.
Kolo was assigned by Jovoni I to be ruler before he died, but Jovoni XII was too powerful and took over. After Jovoni XII died, Kolo became ruler of JoJoLand.
Dagles is also known as Dangles, and he is the current secretary of JoJotown. He greatly assists JoJo with the responsibility of ruling JoJotown.
Ollie is the inventor of the most commonly-said one-word phrase in JoJoLand, "Whoo!". He is the son of Jovoni XII's best friend, therefore knowing JoJo since they were children.
Jovoni VII and Purple Wills
Jovoni VII was (quite obviously) the seventh in the Jovoni dynasty. Purple Wills was a dictator of Willyville. The two leaders fought the War of the Ancients.
Dolo is Kolo's brother and the current assistant leader of JoJoLand.