丁噹啃原本是練游泳，
Duncan is the only son of Ione Duncan, a midwife, and William Duncan, a mason, and has two older sisters, Cheryl and Tricia. He was born and raised in Christiansted, a town on Saint Croix, one of the main islands composing the United States Virgin Islands. In school, Duncan was a bright pupil and dreamt of becoming an Olympic-level swimmer like his sister Tricia.[5][6] His parents were very supportive and Duncan excelled at swimming, becoming a teenage standout in the 50, 100 and 400 meters freestyle and aiming to make the 1992 Olympic Games as a member of the United States Team.[5]

When Hurricane Hugo destroyed the island's only Olympic-sized swimming pool in 1989, Duncan was forced to swim in the ocean and he quickly lost his enthusiasm for swimming because of his fear of sharks.[5] Duncan was dealt another emotional blow when his mother was diagnosed with breast cancer and died one day before his 14th birthday.[5] In her last days, she made Duncan and his sisters promise to finish college with a degree, which would later explain Duncan's refusal to leave college early.[7] Duncan never swam competitively again, but was inspired by his brother-in-law to turn to basketball.[7]