According to the Wikipedia, Malcolm IV (c. 1141 - December 9, 1165) was the eldest son of Henry, Earl of Huntingdon (d. 1152), son of King David I, and succeeded his grandfather David as king of Scotland in 1153. He was called the "Milk Maiden," (possibly because he was believed to have been utterly chaste throughout his life, as the result of a vow) and died unmarried and childless in 1165.
Not much is known of him, but he appears to have been an ineffective monarch. He came to the throne at 11, having been in England as a child. Curiously (for Scotland) his was an unchallenged accession, but his reliance on Norman advisors, rather than Scots lords, caused some disquiet. He has been attacked for surrendering the counties of Cumberland and Westmorland to his cousin, Henry II of England, in return for confirmation of his succession to the earldom of Huntingdon, but the contemporary sources do not appear to indicate that in doing so he was seen as compromising his kingship, although his nobles resented the loss of two counties, and began to plot against him. In 1159 he went with Henry to the French wars, and was at the siege of Toulouse. When he returned, six of his Earls, who disapproved of Scots involvement in England's wars, besieged the king in Perth castle, but ecclesiastical intervention led to a reconciliation.
Though not evident at the time, he was also the last Scottish monarch to have a Scottish name. He was also the king who made the office of Steward of the Royal House hereditary, in family of Walter Fitz-Allen. From Walter came eventually the House of Steward/Stuart who were take the Scots throne from 1371, and the English from 1603.