His parents were Thomas Boyd, Earl of Arran, and Mary, eldest daughter of King James II.
[1] In 1482, on the death of his grandfather, although a minor, James became the titular head of the Boyd family.
[2] He was however sasine of various lands, on three different dates in October 1482, as James Lord Boyd, and was witness to a charter on January 1484 under the same designation.
According to Boyd of Trochrig, "in ipso adolescentis flore periit inimicorum insidiis circumventus" (In the very young flower cut off, the enemy plots).
James was unmarried, and on his death, Kilmarnock reverted to the Crown.