Hello -
I found some genealogy info on Alapai and most of the chiefs on
http://www.hawaiian-roots.com/chiefgen.htm There were also a couple books - they look like they may be hard to find (or out of print) but looks like they have a lot of info. - Pratt, Elizabeth Kekaaniauokalani. History of Keoua Kalanikupuapa-i-kalani-nui, Father of Kings, and His Descendants, with Notes on Kamehameha I, First King of All Hawaii. Honolulu, T.H., 1920
I hope this helps
Sincerely
Darcie