Derek's childhood best friend was Mark Sloan, who came from a wealthier but emotionally deficient background, and was like a second son to the Shepherd family.
As a result he is especially cynical when treating criminals and feels that they do not deserve any compassion from him.
He was raised by a single parent, being his mother Carolyn, along with his four sisters: Nancy, Kathleen, Liz, and Amelia. His father owned a shop when he was younger, and one day two robbers approached him and demanded that he give up the watch his wife Carolyn had saved tirelessly to buy for him.
As a child, Derek had no hair products, so he had a large afro, acne, a weight of 110 pounds, and played the saxophone in the school band.
("Where the Wild Things Are") When the Date and Tell policy was implemented, Rose asked what they meant. ("The Becoming") Derek started avoiding Rose after they had sex, though he claimed it was just because he lost a patient.