He was born in Denbigh, Wales. His mother, Betsy Parry, was nineteen years old at the time of his birth. According to Stanley himself, his father, John Rowlands, was an alcoholic; there is some doubt as to his true parentage.
The parents were unmarried, so his birth certificate refers to him as a bastard, and the stigma of illegitimacy weighed heavily upon him all his life. He was raised by his grandfather until the age of five.
When his guardian died, the boy was sent to St. Asaph Union Workhouse, where overcrowding and lack of supervision resulted in frequent abuse by the older boys. He stayed until the age of 15.
After completing an elementary education, he was employed as a pupil teacher in a National School. In 1859, at the age of 18, he made his passage to the United States in search of a new life. Upon arriving in New Orleans, he became friendly with a wealthy trader named Stanley, whose name he later assumed.
http://en.wikipedia.org/wiki/Henry_Morton_Stanley