John Leland was a United Federation of Planets Starfleet line and flag officer on active duty in at least the 23rd century.
Leland was the older brother of Leonard McCoy's wife Jocelyn, and a law student in Atlanta at the same time McCoy was a medical student.
Some years later, when war broke out between the Federation and both the Kzinti and the Klingons, Leland applied for the four-year command training regimen at Starfleet Academy. Upon graduation, Leland rose up through the ranks quickly, becoming an admiral in charge of the budget for many Starfleet divisions, including Starfleet Medical, by 2269 or '70. (Absolute Horizon)
- It seems more probable that Leland was only a rear admiral (lower half), aka commodore, by his early 40's (and after only 10-11 years post-Academy), but he is called an admiral in Absolute Horizon.