What qualifies one as 'legal step-father'? Obama's mother and Soetoro separated in 1972 and divorced in 1980. By the time he enrolled in Occidental, Obama had been living back in the U.S. for 8 years. So if your definition of step-father is he was married to Obama's mother then I suppose that's true. If you attach some other meaning to it then I'd be curious to know what.