This little American girl, Ann Dunham [1942-1995], had an ancestor named Mary Kearney.
Meanwhile, this little Aussie girl, Kathleen Walker [1918-2003], also had an ancestor named Mary Kearney. However the two Marys belonged to different generations, separated by half a century.
Jumping back in time to the end of the 18th century, we find that the Kearney ancestors of both girls were Irish. Ann Dunham had an ancestor Joseph Kearney, born around 1794 in Co Offaly (province of Leinster). One of Kathleen Walker's ancestors was a Michael Kearney, born around 1785, probably in nearby Co Clare (province of Munster). Admittedly, Kearney is not an unusual surname in Ireland. Nevertheless, with a minimum of speculation (which remains an essential ingredient in genealogical research), one could well imagine that these Kearney males were cousins, if not brothers.
Let's jump forward in time, to 1961. In Hawaii, Ann Dunham married a Kenyan gentleman named Barack Obama. This photo shows Ann holding their son named Barack Obama II, born on 4 August 1961:
As for the other little girl, Kathleen Walker, she was my mother.
It's a fact that both Ann Dunham and Kathleen Walker, brought up in continents on opposite sides of the Pacific Ocean, can be identified as great-granddaughters of Kearneys settled in south-west Ireland at the end of the 18th century, within a radius of a hundred kilometers or so. As I've pointed out proudly in chapter 4 of my monograph entitled A Little Bit of Irish [display], the Kearney ancestors of my mother Kathleen Walker lived in the legendary village of Spancil Hill.