BUENOS AIRES, Argentina (AP) — Martin Ogando and his 91-year-old grandmother, Delia Giovanola, flip through a stack of photos until they reach an image of a man Ogando never saw in life: his father.

The two share similar skin tone and blue eyes — products of the same genetics that finally allowed Ogando to discover his birth identity through DNA tests in November 2015.

The tests showed that he's the biological son of Jorge Ogando and Stella Maris Montesano, a child born in captivity in a clandestine detention center and taken away from parents who were forcibly disappeared in 1976 during Argen...