Who is Joseph and Sarah from Sacred Journey of the Peaceful Warrior and what is their importance?

Joseph and Sarah are residents of Molokai Island and close neighbors of Mama Chia, Joseph and Sarah hear about Dan Millman washing ashore in bad condition from their precocious daughter, Sachi, Mama Chia's huna apprentice. When he finally meets Sachi's parents, he is shocked to see an old friend - the owner of a small café in Berkeley, CA, one of Socrates' students, whose tales of Mysore, India, earlier lead Dan there on his spiritual quest. Dan had heard that Joseph died of leukemia.