Captive White Boy: The captive white boy, Santiago McKinn, poses with a group of children in Geronimo's Camp. This photo is a detail from a larger image. Behind him is a partially constructed tent. The photo by Camillus Sidney Fly was taken in 1886 shortly before Geronimo's surrender to General George Crook on March 27, 1886. McKinn was taken from his home near Mimbres in the New Mexico Territory in 1885 by Chiricahua Apaches. McKinn assimilated with the Apaches during his captivity -- even learning their language -- and cried when he was returned to his family.
GERONIMO'S YOUNG CAPTIVE
New York Times / March 30, 1886
WILLCOX, Arizona, March 29. -- With the Chiricahuas under Geronimo was a white boy, aged 10 years. He says his name is Santiago McKinn, and that his father is Irish and his mother Mexican; that he was captured near Mimores, New-Mexico. He has light hair, gray eyes, and is of light build. He says the indians treated him kindly.
A more detailed account of the McKinn story can be found on Desert Exposure.