Worf
Worf is the first klingon in Starfleet. He was raised by adoptive human parents, the Rozhenko familys after his Klingon father, Mogh was killed in by a Romulan attack on the Klingon colony Khitomer.
Military history
He was assigned to the Enterprise-D as a Lieutenant Junior Grade. Upon the death of Natasha Yar, he was given her former position of chief of security. He eventually transfered to Deep Space Nine and has advanced to the rank of Lieutenant Commander.
Worf feels exceptional loyalty to his "klingon heritage" and has diverted his a fair portion of his time in starfleet to deal with problems facing the Empire, including the threat of the Duras family, and Gowron's inept leadership of the Empire during the Dominion war.
Personal life
Worf fathered a son with the half human/half klingon K'Ehleyr, Alexander Rozhenko. Alexander came into Worf's life when K'Ehleyr died. Relations between Worf and Alexander have been strained and Alexander has been bumped around between staying with Worf and the Rozhenkos. Late in TNG he began a short-lived romantic interest with Deanna Troi. While on DS9, he married Jadzia Dax, but she too died. After Jadzia's death, he breifly entertained the idea of a relationship with Dax's subsequent host Ezri but it quickly ended.
He also feels a stong need to "be true to his klingon heritage" and engages in their masochistic rituals on a regular basis. He does not take kindly to insults and his favorite human food is prune juice.