He was a child when his father, King Duncan, was slain by Macbeth (1040). He spent his youth in Northumbria with his uncle, Earl Siward, who in 1054 established him in Cumbria and Lothian. 
In 1057, after Macbeth was slain, he became King of all Scotland. His first wife, Ingibiorg, widow of Thorfinn of Orkney, had died; and in 1069 Malcolm wedded Margaret, sister of Edgar the Aetheling, whose cause he made his own. 
Five times he harried Northumbria (1069, 1070, 1079, 1091, 1093) and there were counter-invasions by William the Conqueror and Prince Robert in 1072 and 1080. In 1092 William II Rufus wrested from Scotland all of Cumbria south of the Solway; and next year Malcolm 
marched into England but was entrapped and slain at Alnwick on 13 November 1093. He left five sons, of whom four succeeded him: Duncan, Edgar, Alexander and David. 
 

Source: Leo van de Pas