John Colton's blog

I thought this was interesting:

http://www.suite101.com/content/president-barack-obamas-mormon-ancestry-a295278

President Obama is a great-great-grandson of Nancy Ann Childress Osburn Armour Turner, who was a member of the Reorganized Church of Jesus Christ of Latter Day Saints (RLDS).

Genealogical research reveals that the much-married Nancy Ann Childress (1848-1924) is President Barack Obama’s Mormon ancestor. She married 1) James Osburn in 1868, 2) George W. Armour (ca. 1849-1889) in 1871, and 3) James T. Turner who had previously married Nancy’s sister, Sarah Catharine. Nancy and James were wed in 1897.

Nancy was born in Clark County, Missouri, the daughter of John Milton and Nancy (Conyers) Childress. (In some records the surname is spelled Childers.) She died in St. Mary’s Township, Hancock Co., Illinois. Both of her parents had been born in Kentucky. Her three marriages all took place in Lewis, County, Missouri and there is no indication that any of them were bigamous.

Nancy joined the RLDS Church after the death of her second husband. In February of 1877, James and Sarah Turner – Nancy’s third husband and her sister – had became members of the Reorganized Church of Jesus Christ of Latter Day Saints, and both of them remained true to their conviction of the gospel restored by Joseph Smith to the end of their lives.

(there are some more details at the link, if you're curious)