The estate of Lybster is in the parish of Reay.
Before the rise of the Sinclairs of Lybster, in Latheron, there were Sinclairs of Lybster, in Reay, dating from at least 1636. Their origin is uncertain, but it is conjectured that they may have been the descendants of Henry Sinclair, who died about 1614, a natural son of John, Master of Caithness, and who got from his brother, the Earl of Caithness, a wadset of Downreay and part of Lybster. Or possibly this family may have been of the Sinclairs of Dunbeath, who held Downreay and other lands in Reay.
In 1636 there is mention of DAVID SINCLAIR OF LYBSTER and, in 1638, of WILLIAM SINCLAIR OF LYBSTER, who then appears as witness to a deed by Oliver Sinclair of Spittal, son of Richard of Brims, and grandson of William Sinclair of Dunbeath. David and William were probably brothers, each inheriting a portion of Lybster. William had a daughter, Margaret, who, as heir to her father, executed a renunciation, in 1648, in favour of her cousin, James Sinclair of Lybster.
David Sinclair of Lybster had two lawful sons:-