David McCoy was a male Human in the 23rd century. (Star Trek III: The Search for Spock) He was the father of Doctor Leonard McCoy, chief medical officer of the USS Enterprise, and grandfather of Joanna McCoy. (Star Trek III: The Search for Spock; TAS: "The Survivor")
David, like previous generations of McCoys, passed down the family recipe for Southern baked beans to his son, Leonard. Years later, Leonard revealed that the "secret ingredient" was Tennessee whiskey.
Late in his life, David was stricken with an incurable painful disease and begged his son to help him end his life. A cure was discovered soon after, subsequently causing Leonard many years of regret from causing his father's apparently needless death.
This character, whose first name is established in Star Trek III: The Search for Spock, was named after the father of Leonard McCoy actor DeForest Kelley. He recalled that, originally, the character was to have been given the first name "Leonard" and that it was only at his urging that this was changed to "David". Some people assumed Kelley was attempting to reference the Biblical character of King David, when, in reality, Kelley actually intended the name as a reference to his own father. (From Sawdust to Stardust, pp. 257-258)
The same issue of Star Trek: Ongoing relates David's alternate reality counterpart healing a broken arm that a young Leonard sustained after falling out of a tree. Later, after his divorce, Leonard discusses with his father how his ex-wife (β) took everything he had.
The novel More Beautiful Than Death establishes that the Kelvin Timeline counterpart of David McCoy died while Leonard was in medical school.