Of his father, Alpin, little is known, though tradition credits him with a signal victory over the Picts by whom he was killed three months later (c. 834). Kenneth succeeded him in Dalriada and ruled in Pictavia also, ruling for 16 years. The period is obscure. The gradual union of the two kingdoms from 843 doubtless owes much to intermarriage. By the Pictish marriage custom, inheritance passed through the female. Nevertheless, Kenneth probably made some conquests among the eastern Picts and possibly invaded Lothian and burned Dunbar and Melrose. After attacks on Iona by Vikings he removed relics of St. Columba, probably in 849 or 850, to Dunkeld, which became the headquarters of the Scottish Columban church. He died at Forteviot, not far from Scone in Pictish territory, and was buried on the island of Iona.

Constantine's reign was occupied with conflicts with the Norsemen. Olaf the White, the Danish king of Dublin, laid waste the country of the Picts and Britons year after year; in the south the Danish leader Halfdan devastated Northumberland and Galloway. Constantine was slain at a battle at Inverdovat in Fife, at the hands of another band of northern marauders. His heir was his brother Aed, who was killed by the Scots after a year and was succeeded by a nephew, Eochaid.

His reign coincided with renewed invasions by the Danes, who came less to plunder and more to occupy the lands bordering Scotland and the Anglo-Saxon kingdoms. He was also embroiled in efforts to reduce the highland robber tribes. By one account he was slain at Dunnottar, meeting a Danish invasion; by another he died of infirmity brought on by his campaigns against the highlanders. He was succeeded by his cousin Constantine II.

Malcolm succeeded to the crown when his cousin Constantine II entered a monastery (943). He annexed Moray to the kingdom for the first time. After driving the Danes from York, the English king Edmund turned Cumbria over to Malcolm, apparently as a fief or seal of alliance. Later, when Norsemen again invaded the land, the Scots sent raids against the English, and in 954 the West Saxon king Eadred reunited the northern counties to his dominions. Malcolm was slain the same year.

He began his reign by ravaging the Britons, probably as an act of vengeance, but his name is also included among a group of northern and western kings said to have made submission to the Anglo-Saxon king Edgar in 973, perhaps at Chester; and the chronicler Roger of Wendover (Flores Historiarum, under the year 975) states that shortly afterward Kenneth received from Edgar all the land called Lothian (i.e., between the Tweed and the Forth rivers). This is the first mention of the River Tweed as the recognized border between England and Scotland. Kenneth was slain, apparently by his own subjects, at Fettercairn in the Mearns.

Malcolm succeeded to the throne after killing his predecessor, Kenneth III, and allegedly secured his territory by defeating a Northumbrian army at the battle of Carham (c. 1016); he not only confirmed the Scottish hold over the land between the rivers Forth and Tweed but also secured Strathclyde about the same time. Eager to secure the royal succession for his daughter's son Duncan, he tried to eliminate possible rival claimants; but Macbeth, with royal connections to both Kenneth II and Kenneth III, survived to challenge the succession.

Duncan was the grandson of King Malcolm II (ruled 1005-34), who irregularly made him ruler of Strathclyde when that region was absorbed into the Scottish kingdom (probably shortly before 1034). Malcolm violated the established system of succession whereby the kingship alternated between two branches of the royal family. Upon Malcolm's death, Duncan succeeded peacefully, but he soon faced the rivalry of Macbeth, Mormaor (subking) of Moray, who probably had a better claim to the throne. Duncan besieged Durham unsuccessfully in 1039 and in the following year was murdered by Macbeth. Duncan's elder son later killed Macbeth and ruled as King Malcolm III Canmore (1058-93).

Malcolm acknowledged the overlordship of William in 1072 but nevertheless soon violated his feudal obligations and made five raids into England. During the last of these invasions he was killed by the forces of King William II Rufus (reigned 1087-1100). Except for a brief interval after Malcolm's death, the Scottish throne remained in his family until the death of Queen Margaret, the Maid of Norway, in 1290. Of Malcolm's six sons by Margaret, three succeeded to the throne: Edgar (reigned 1097-1107), Alexander I (1107-24), and David I (1124-53).