Just like DeForest Kelley's original version in the Star Trek TV series, Karl Urban's Dr. Leonard McCoy has been an integral member of the U.S.S. Enterprise in the Star Trek reboot movies. It's hard to imagine James T. Kirk, Spock and the rest of the gang traveling to strange new worlds, and seeking new life and new civilizations, without McCoy around as the Chief Medical Officer. That being said, the new Star Trek movies have barely delved into McCoy's personal life, so if/when Star Trek 4 gets off the ground, Urban is hopeful that the next installment will involve the family McCoy's been separated from for years. The actor stated:
Perhaps it would be interesting to see something of McCoy's family. His ex-wife and daughter and that dynamic.
After reaffirming how he and his Star Trek costars are waiting for Paramount Pictures to make a decision on Star Trek 4 one way or another, Karl Urban provided the above answer at the Continuing Voyage Convention in Chicago this past Saturday (via TrekMovie) when asked by a fan about what he'd like to see happen with his character in the fourth movie. As Leonard McCoy revealed to Kirk when they first met in 2009's Star Trek, he went through a particularly rough divorce with his wife, and the only reason he joined Starfleet is because she took everything expect his bones. No mention was made of McCoy's daughter (Joanna, if she has the same name as her Original Series counterpart), so if it's been years since he's seen his child, that certainly would make for an interesting side plot in Star Trek 4.
Despite Star Trek 4 not officially being greenlit yet, a short synopsis was revealed last year shortly before Star Trek Beyond's release. The next installment will see Chris Hemsworth returning to the franchise, as James Kirk will reunite with his father, George, who, in this reality, died in battle aboard the Kelvin on the same day Kirk was born. It still hasn't been clarified how this will be accomplished, though time travel is the most popular guess. Fitting Leonard McCoy's family into such a storyline could be complicated, but considering that the new movies have barely touched on McCoy's life outside of his Starfleet duties, bringing in his ex-wife and daughter would be a good way to further develop his character, especially if Star Trek 4 ends up being the final entry in this series of Star Trek movies.