If this warlike Border family were ever so crabbed and contentious as to deserve their popular description as 'the cappit Kerrs', it was no doubt because of the long contest for supremacy between the two great houses of Cessford and Ferniehurst. Family tradition relates that they were descended from two brothers, without settling the important point of which was the senior. Although for many years the heads of each line alternated in the office of Warden of the Middle March, their rivalry brought death and disorder more than once to the Border. The centre of the family's power lay in lower Teviotdale, but various Kerrs acquired lands in the counties of Peebles, Haddington, Dumfries, Lanark, Stirling and even Aberdeen in the reign of David II. While probably of the same stock, all families of the name in Scotland do not necessarily descend from the two contending houses.
First of the name in Border history was John Kerr, "hunter" at Soonhope near Peebles, who emerges towards the end of the 12th century. John Kerr of the forest of Selkirk acquired Altonburn in 1358, and the second Andrew of that place had a crown charter of the lands and barony of Cessford in 1467. The castle of Cessford - impressive even in ruin - stood on the bank of a hill stream running into the Kale water near Morebattle, on the northern edge of the Cheviots. Meantime Thomas Kerr of Smailholm, apparently a younger son of Cessford, got Ferniehurst by marriage, with its castle (now replaced by a later building) on the wooded banks of the Jed. They were only six miles apart and about the same distance from the English Border.
Family quarrels were not the only cause of trouble among the Kerrs. A few years before Flodden three Englishmen killed Sir Robert Kerr, a former warden of the middle march, while he was attending a march across the Border, and his son tracked down one of the murderers and gave him what was known as "Jeddart justice". After Flodden some of the Leddesdale clans put themselves under Ferniehurst's protection, but in 1523 his castle was taken by the English after a bold defence. Cessford, who had worked as warden for peace and co-operation with England, was killed by a follower of Scott of Buccleuch in the attempt to rescue James V from the Douglases. The two Kerr houses sank their differences then, and again in 1545 so that their feud should not weaken the defense of the Border against the English. But Scotts and Kerrs continued to raid each other's lands, and in 1552 Buccleuch was murdered in Edinburgh by Cessford and some others. The Privy Council managed to patch up the quarrel, with Cessford promising to 'bury the past in oblivion and live in amity in the future' with the Scotts, and a solid phalanx of lairds of both names agreed to ride together against trouble-makers, 'Scot with Ker and Ker with Scot'. Not until two more Kerrs had been killed, including a laird of Ancrum 'expert beyond others in the laws and customs of the Borders', was the feud settled by a mumble apology from Cessford and payment of 10,000 merks, followed by 'letters of slains' in forgiveness from the murdered man's sons. As the long-standing national rivalries also came to an end, one of the last of the 'general bands' against Border thieves and aggressors was signed in 1602 by five Kerr lairds in Jedburgh and two more in Peebles.
Union with England under one crown reduced the importance of Border clans and groups, but by now the principal Kerrs were influential magnates. Two of them followed the court to London, and royal flavour was reflected in a series of honours - Cessford was made Lord Roxburghe (1600), earl (1616) and duke (1707), while Ferniehurst became Lord Jedburgh (1622) and through a cadet branch Earl (1631) and Marquess (1701) of Lothian.