He was a fellow communist. In Honolulu at that time, early 1960’s, probably every communist in town knew all the other communists in town.
Professor Gerald Horne, a contributing editor of the Communist Party journal Political Affairs, talked about it during a speech last March at the reception of the Communist Party USA archives at the Tamiment Library at New York University. The remarks are posted online under the headline, “Rethinking the History and Future of the Communist Party.”
Horne, a history professor at the University of Houston, noted that Davis, who moved to Honolulu from Kansas in 1948 “at the suggestion of his good friend Paul Robeson,” came into contact with Barack Obama and his family and became the young man’s mentor, influencing Obama’s sense of identity and career moves. Robeson, of course, was the well-known black actor and singer who served as a member of the CPUSA and apologist for the old Soviet Union. Davis had known Robeson from his time in Chicago.
As Horne describes it, Davis “befriended” a “Euro-American family” that had “migrated to Honolulu from Kansas and a young woman from this family eventually had a child with a young student from Kenya East Africa who goes by the name of Barack Obama, who retracing the steps of Davis eventually decamped to Chicago.”
Google is your friend.
http://www.amazon.com/Communist-Paul-Kengor/dp/1451698097
also:
http://theconservativetreehouse.com/2012/06/20/oh-my-ann-dunham-pictures-surface-president-barack-obamas-mom/