On the 2nd October 1545, the Master [heir apparent] of Caithness obtained a charter from Queen Mary, by which the Earldom became a male fee to him and his heirs male. At Edinburgh, on the 1st December 1565, he protested that his father should not be required to answer citation obtained by William Sutherland (Hectorson) in Berriedale, etc. Protests admitted, and their renewed complaints on 31st January thereafter were refused. In 1567 he stormed Dornoch, and his father's mal-treatment of the hostages then taken - in violation of the terms of surrender - was the foundation of the hatred between sire and son, which ended in the Master's death.
Upon his imprisonment in Girnigo Castle there were three keepers appointed over him, namely, Murdoch Roy, and two brothers, Ingram and David Sinclair. Roy was the one who regularly attended him and performed all the menial services connected with the office. The other two, who were kinsmen of the Earl, and are stated to have had a bend sinister in their escutcheon, might be said to be inspectors or head gaolers. Roy, it would appear, was not altogether a hardened miscreant, steeled against the ordinary feelings of humanity. His heart was touched with pity for the unfortunate nobleman, and at the earnest and oft-repeated solicitations of the latter, he agreed to endeavour to set him at liberty. Unfortunately the scheme was discovered by John's brother William, who bore him no goodwill, and at once informed his father of the meditated escape. The Earl forthwith ordered Roy to be executed, and the poor wretch was immediately brought out and hanged on the common gibbet of the castle, without a moment being allowed him to prepare for his final account.
Soon after, William Sinclair of Mey visited the cell, and the brothers had an angry altercation. Embittered by the bad usage and long confinement he had endured, the Master, a man of powerful physique, and therefore called Garrow or the Strong, though heavily fettered, sprang upon his brother and actually crushed out his life in an iron embrace. [From History of Caithness].
This deepened the father's antipathy to his unhappy son. He had now been nearly six years in duress, and it is stated that his keepers, the two Sinclairs, instigated by the Earl, deliberately compassed the death of the poor captive, and that by a most inhuman method. They first withheld food from him for a few days, and then supplied him abundantly with salt beef, of which, in his famished state, he ate voraciously. A raging thirst came upon him, but his brutal keepers denied him water, and left him to die in writhing agony. The accounts of his death differ as to details, but all agree that he was barbarously murdered. His remains were interred in the "Sinclair Aisle" in the churchyard of Wick, which his father had built some years before. The inscription on the stone over his grave is most legible. It reads: "Here lies entombed an noble and worthy man, John, Master of Caithness, who departed this life the 15th day of March 1576" [From Calder Scenes and Stories]
He married Jean, Lady Morham, daughter of Patrick Hepburn, Earl of Bothwell, who makes supplication in April 1581, on behalf of her lawful son, Francis Stuart, Earl of Bothwell.
NOTE - Alliances with the Hepburns of Bothwell invariably resulted in unruly issue. Examine the career of the descendants of the Earls of Bothwell in the direct male line and in the descendants of Jean, Lady Morham, for which latter see the Caithness family, that of Sinclair of Underhoull, Shetland, Bruce of Sumburgh, and Stuart, Earl of Bothwell.
By her he was father of -
NOTE - Agnes Sinclair, sister or daughter of John, Master [heir apparent] of Caithness, married, first, Andrew, seventh Earl of Errol; second, Alexander Gordon of Strathdon. [Henderson]The Master had also two natural sons -
A Henry Sinclair, servant to the Earl of Caithness, appears 5th January 1615, in the jury empannelled to try Robert Stewart, base son of Patrick, late Earl of Orkney. [Pitcairn's Criminal Trials]
NOTE - The continual contention between the leading families in Scottish Orcadia is well exemplified in the still current couplet:
"Sinclair and Sutherland, Keith and Clan Gunn,
There never was peace where these four were in."
The reference is to the Earls of Sutherland, and not to the family, which is found to be always at amity with the Sinclairs.