After his parents were killed in a Romulan massacre, Worf was raised by humans and became the first Klingon in Starfleet. He was promoted to Chief of Security in TNG's first season, following Tasha Yar's untimely death. Worf later leaves the Enterprise to join Deep Space Nine.
Wesley lost his father at a young age and was raised alone by his mother, Beverly Crusher. Both of his parents had been acquainted with Captain Picard long before Wesley came aboard the Enterprise. Extremely intelligent and dedicated, Wesley eventually gains a field commission of Ensign before leaving to attend Starfleet Academy.
While endeavoring on his personal goal of being more human, Data is indispensable to the Enterprise, serving as its second officer and chief of operations.
Blind since childhood, LaForge uses his impressive technical knowledge as Enterprise's Chief Engineer. He originally joined Enterprise as helmsman, LaForge is promoted in TNG's second season.