Joan was born about 1404 CE, she was a half niece to Henry IV and great- granddaughter to Edward III. When she was about 16, in 1420, James I of Scotland saw her while he was imprisoned and she was walking in the garden. She was the object of a love poem he wrote while imprisoned at the Court of Windsor, The Kingis Quair.– http://d.lib.rochester.edu/teams/text/mooney-and-arn-kingis-quair-and-other-prison-poems-james-i-scotland-kingis-quair. He had dropped her a rose one day and she wore it to dinner the next evening. She then pled to have him released. He was released after both his uncle and Henry V died and marrying Joan was one of the terms of his release. “James and Joan were married at the Church of St Mary Overie, Southwark, on 2nd February 1424. James was released on the 28th March and the couple returned to Scotland shortly after. They were crowned at Scone by Henry de Warlaw, Bishop of St Andrews, on 21st May 1424.”1

The two ruled together for 13 years and she often made decisions with him. She was also known to plead for those who were to be executed. When his enemies killed him (and injured her) she ruled on behalf of their son James II as Regent. When she remarried, this time to Sir James Stewart (Yes, same name as her first husband) she was arrested by Alexander Livington and charged with kidnapping the king, her son. She was only released upon agreeing to leave court and by giving up custody of James.

She died at Dunbar Castle owing to the ongoing unrest with Livingston on July 15, 1445 and was buried at Carthusian Priory at Perth alongside King James.

Sources

http://d.lib.rochester.edu/teams/text/mooney-and-arn-kingis-quair-and-other-prison-poems-james-i-scotland-kingis-quair

https://en.wikipedia.org/wiki/Joan_Beaufort,_Queen_of_Scots

James I and Joan Beaufort: A Royal Love Story

Joan Beaufort, Queen of Scots

http://www.undiscoveredscotland.co.uk/usbiography/b/joanbeaufort.html