We have the divorce papers, and people who were never legally married don't get divorced. And long-established law is that the child of a marriage is the legal child of both partners of the marriage, no matter who the biological father is.
I’m fully aware that of the law regarding legal paternity.
As for the “marriage,” documentation may someday turn up. I doubt it, considering Obama’s effort to pre-emptively explain it away in his book, admitting the details are hazy.
The divorce papers would be necessary, regardless of whether there had been a marriage ceremony, because Ann had been passing the kid off as the son of a marriage (common-law or otherwise) for years.
She needed to establish legal custody. She had plans to marry Soetoro and let him adopt the boy. Can you imagine the hassle of getting Sr.’s signature on all the paperwork required, both in Hawaii and Indonesia, for adoption, citizenship, school, etc. if the court had not awarded her sole custody? She was just taking care of business.