However, legally, if Obama Senior was married to Ann Dunham, at the time of birth, Obama SR is the legal Father, no matter what!
Getting the birth cert out of Hawaii might be easier than getting the marriage certificate out of London....
Even if he is a bigamist and his marriage to Dunham is void?
I would say that he is the biological father, and if that's what you mean by "legal," I'm in agreement - and that has nothing at all to do with marriage.