You can cut this any way you like. The theory that his father is Frank Davis is as plausible as any other. Additionally the fact that BHO Sr. was ALREADY MARRIED IN KENYA would invalidate any marriage in Hawaii.
Marriage in Kenya was a tribal ritual and not a legal marriage....Common law kind of thing. Kenya also allows multiple marriages.
As to the biological father: all state recognize the spouse as the legal father whether or not they are the biological father. First hand experience with my step children...Their mom tried to deny visitation on grounds kids were not biologically her husbands....all it got her was having custody denied to her.