#1 Robert Kinloch Massie III (b. 1929), historian, author of Nicholas and Alexandra.
#2 Robert Kinloch Massie, Jr. or IV (b. 1956), son of #1; social activist, Episcopal priest, author of Loosing the Bonds.
The Library of Congress lists only two authors called Robert Massie, both of whom are called Robert K. (Robert Kinloch) Massie; they are father and son and should have separate LT author pages.