Robert the Bruce was born in 1274 into a noble family in Scotland. He received the Earldom of Carrick from his mother and his father had claims to the Scottish throne.
When William Wallace wanted John Balliol to become king, Robert and his father saw him as a person who would seize the throne, so they sided with Edward I. After Edward I took over the throne, he wanted to rule the whole country, but Robert couldn't stand a chance against his own people, so he sided back with William Wallace and his band.
William gave Robert the position of Guardian of Scotland, which gave Robert some support, but John Comyn, John Balliol nephew, also had a strong claim.
Robert had trouble gaining the approval of the Scots because he sided with Edward before. But John met with Robert and agreed to resign his claim on the throne if Robert would give his land to him. But then Comyn didn't resign so Robert killed him in a duel.
After the duel, he could either become a fugitive or become king. So he fought for the throne and claimed the castle at Dumfries. Then 6 weeks late he became was crowned king in, March 26, 1306.