One of the main issue, IMO, is whether the parents are married or not. I don’t know about American law, but in many countries a child born of unmarried parents is more likely to follow the mother’s citizenship.
Right. It's weather or not Sr. is his real father...and weather or not Sr. and SADO were legally married in HI.
However, at this point, we have Barry's word (for whatever it's worth) that Sr. was his father...and we have court documents from the state of Hawaii that state they were legally married.
Barry's Parents Divorce
The 1964 divorce record from the Circuit Court of the First Judicial Circuit State of Hawaii, states that Stanley Ann D. Obama and Barack H. Obama "were lawfully married in Wailuku, Maui, State of Hawaii, on February 2, 1961, by a person duly authorized to perform marriage cerimonies and ever since that date have been and are now husband and wife." http://www.scribd.com/doc/18130289/Obama-1964-Divorce-Papers-13-Pages-Missing-Pg-11
So until it's proven in a court of law, that his parents weren't who he say's they were, or that they weren't legally married...this is what we have at this point. They were legally married in HI.
Yes, I did read about a difference depending on whether the parents were married. I can’t remember the exact details now, but I think the unwed mother only had to be in the US for the 1 year prior to the birth for the child to be a citizen.