Mamma got knocked up at 17.
Had Barry when she was 18.
had to be 19 under the “naturalized” rules in place at that time- 1961.
JMHO, I think her marriage to Obama Sr. was bigamous and therefore null and void under U.S. law, so she wasn't "married" in the first place. Barry Jr. is the illegitimate issue of a U.S. citizen, but therefore a natural-born citizen nonetheless regardless of birthplace. There is no Kenyan issue.
There is, however, a big, fat Indonesian issue that hasn't been addressed, either.