Constantine II of Scotland

Constantine II (870s - 952) was the first king of Alba, he ruled from the year 900 until his abdication in 943. He was the son of Áed, king of Scots who ruled from 877-878. He was succeeded by his 1st cousin once removed Malcolm in 943 when he abdicated. He died in 952.
Birth.
Nothing apart from the fact that Constantine's birth happened in Scotland is known about it, although it may of happened in Iona, Scotland in the 870s.
Reign.
His reign began in the year 900 when he succeeded his cousin Donald II of Scotland and would continue to reign for 43 more years. In 904 he defeated Vikings at the Battle of Streathearn. He oversaw the founding of England by king Æthelstan in 927. He is defeated by Æthelstan in 937 who proclaims himself king of Britain. People in Scotland, Wales, England and Ireland began to cal Æthelstan our father and our lord, and our king. He died in 939 and by 943 Edmund I of England began to invade Scotland to rule the whole of Britain. Constantine, scared of being killed abdicated. Proclaiming he could not handle the English forces. 
After his reign.
After he abdicated, Constantine decided to become a monk, and moved to a monastery in St Andrews, Fife. 11 years later he dies childless, passing the throne to his 1st cousin once removed Malcolm I who ruled until 954, 2 years after the death of Constantine.