Obama says in his autobiography that he never took the time to nail down whether his parents were actually married. Given his penchant for shading the truth, I suspect what that really means is that he found out they were never married but does not want to admit it.
It makes no sense to me that an attorney obsessed with his background would have made no such effort, especially given how simple it would have been while he was working at a law firm.
Obviously the only way to know for sure is to visit the HI courthouse and search the records for evidence of the Obama divorce. If it's not there, they were never married.
I don’t know that something like that would even matter now- I just mentioned it because it is interesting what used to be put on BCs. I was pretty serious about genealogy for a few years and it is amazing the way things were done “back in the day” on different documents.