William, 1st Earl of Douglas, was an interesting character, from a genealogical perspective. Of relevance to this topic, his children George, Margaret and Isabel Douglas were brothers and sisters, but not by the same mothers. Even more interesting is that George, who became the 1st earl of Angus, was seen as the product of incest as his mother was the widow of Earl William's wife's brother, Thomas, 13th Earl of Mar.
The following is one theory as to how Bonjedward became a Douglas lairdship. It had previously been in the possession of The Good Sir James Douglas, who was killed in Spain in 1333. Thereafter, it was held at some point by James Sandilands. At that time, Timpendean would have been part of Bonjedward.
Scotland's Historic Heraldry by Bruce A McAndrew
Re George 1st Earl of Angus "...William, 1st Earl of Douglas, had children by his sister in law. Margaret Stewart, Countess of Angus (1417/18), the eldest of whom was named George. He was acknowledged lord of Angus 1389-97 and thereafter earl till his early death soon after the battle of Homildon Hill. He was the progenitor of the Red Douglas earls of Angus, who inherited the estates of Isabel Douglas of Mar. Margaret, sister of George Douglas, married Thomas Johnstone in 1404; their children adopted the name of Douglas and the designation of Bonjedward (ROX); their arms, according to Nisbet, were Argent, a heart gules, in chief a label of three points gules, on a chief azure, three mullets argent..."
However, "Godscroft affirms that the Douglases of Bonjedward are descended from a natural son of George fifth earl of Angus who died in 1462". (It was the 4th earl who died in 1462, Archibald was the 5th earl.)
The lands of Timpendean lying in the territory of Bonjedworth were in 1479 granted by George
Douglas (who may have been killed at Flodden in 1513) with consent of James his son and heir (who inherited Bonjedward) to his son Andrew from whom they descended in lineal succession to William Douglas who held them in 1718.
From here the genealogy of the Timpendean line has been identified. We still have to resolve the Bonjedward line. If they both stem from a Johnson (or Johnston), then we have an interesting situation which, perhaps, dna testing can resolve.
Does anyone have these lines in their family tree?
These are very much work in progress, so the content is liable to change.