John Steel Lewes, known as Jock, was born in Calcutta, India, to British parents. His early life was spent in a comfortable, colonial environment. Though born in India, he would later be educated in Britain and his early experiences likely instilled a sense of adventure and a familiarity with different cultures, traits that would later serve him well in his military career.

Lewes attended Radley College, a prestigious boarding school in Oxfordshire. He excelled academically and athletically, demonstrating leadership qualities and a strong sense of determination. His time at Radley shaped his character and provided him with a solid foundation for his future endeavors.