Lieutenant Colonel David Parkinson, 58, was killed with a machete when the gang, who were also carrying a gun, broke into his house in the early hours of Sunday.
His wife, Sonja, managed to flee and lock herself in a storeroom until the gang had left, only to return and find her husband dead.
The couple were targeted at their Lolldaiga Hills cattle ranch in the town of Nanyuki. Before moving to the ranch, Lt Col Parkinson, served with the Parachute Regiment for 30 years, from 1973 to 2003.
He spent five years as deputy director at the Lewa Wildlife Conservancy, a nearby game reserve.
The Duke of Cambridge spent part of his gap year at the Lewa wildlife reserve, before returning with Kate Middleton in 2005, and again in 2010 where he proposed to her. A spokesman for the Duke said he was saddened to learn of the death of Lt Col Parkinson, whom he had met at the reserve.
Harry Bucknall, who served in the Army with Lt Col Parkinson, said he was "devastated" by the death of "a great friend" and "very special person indeed".
He said: "He was a very special person, whom I loved like a brother, and Sonja a wonderful ray of light."
Police said a suspect was arrested from a nearby village.