The McCoy family, as of the late 23rd century, was comprised of Leonard McCoy, (a doctor in Starfleet aboard the USS Enterprise), his father, David, and Leonard's daughter, Joanna.
The family had a Southern baked beans family recipe that was handed down from generation to generation. The "secret ingredient" was Tennessee whiskey. (Star Trek V: The Final Frontier)
An earlier version of the script for Star Trek V: The Final Frontier named the secret ingredient as Kentucky bourbon.
In the alternate reality, Leonard McCoy had been married at one point, but as of 2255, they had gotten divorced, leaving him with nothing but his bones. (Star Trek)
The Pocket TOS novel Crisis on Centaurus established that McCoy had a married sister, Donna Withers (β), who cared for Joanna.
The TOS comics "Furlough to Fury" and "World Beneath the Waves" gave him another daughter, Barbara McCoy. (β)