They got married in 1961
Stanley Ann Durham was Barrack Obama's grandfather, they did not get married.
Barack Obama's parents, Barack Obama Sr. and Ann Dunham, were married on February 2, 1961.
The mother of President Barack Obama was Ann Dunham (Stanley Ann Dunham 1942-1995). She was married to Obama's father Barack Obama, Sr. and later to Lolo Soetoro, who was Obama's stepfather and the father of his half-sister Maya.
Her birth name was Stanley Ann Dunham; she preferred to be called Ann. When she married her second husband, she was briefly known as "Ann Dunham Soetoro."
President Barack Obama's parents are Stanley Ann Dunham, who was called Ann, and Barack Obama, Sr. Barack, Sr died in 1982 and Ann Dunham died in 1995.
Stanley Ann Dunham was the first name of Barack Obama's mother. After her husband died, she married another man by the name of Lolo Soetoro and changed her name to Stanley Ann Dunham Soetoro. When they divorced in 1980, she then changed her name to Ann Dunham Sutoro.
Ann Dunham
Barack Obama's mother Stanley Ann Dunham, married Barack Obama, Sr. a student from Kenya. She and Barack were married in a private ceremony on February 2, 1961. Her second marriage was to Lolo Soetoro, another East-West Center student from Indonesia. Source: http://www.biography.com/articles/Barack-Obama-12782369 http://www.biography.com/articles/Ann-Dunham-434238
According to the image of Obama's birth certificate at FactCheck.org, her maiden name was Dunham. She was named Stanley Ann Dunham at birth (her father had wanted a son); but she did not like her first name, so she used her middle name, Ann.
Barack Obama Sr and Stanley Ann Dunham
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Her maiden name was Stanley Ann Dunham (she hated her first name, and generally used her middle name as a result). When she married Barack Obama Sr., she became (Stanley) Ann Dunham Obama.