What does the name kian mean?

In Ireland Kian or Cian, pronounced Key-An, was the name of the mythical ancestor of Cianachta in the Irish legend. Kian was also the name of a son-in-law of Brian Boru.

It also has a different meaning, my little brother's name is Kian, and it is also a Persian name

which means "King". Pronounced Kee-yaun.