Centuries before, the English and Scottish thrones were united, there was a time when a little girl named Margaret of Norway was set to become Queen of Scotland following the death of her maternal grandfather, but her succession was contested. When she died at age seven on the voyage to Scotland, clearly without children of her own, the little kingdom was embroiled in a succession war. Had Margaret lived, King Edward I of England, who was hammering the Scots, might have married her to the Prince of Wales and united the thrones 300 years sooner. Instead, the union took place after the first Queen Elizabeth executed her cousin and presumptive heir Mary Queen of Scots for treason and left the English throne to Mary's son King James V of Scotland. As for Mary, who had inherited the Scottish throne when she was six days old, her mismanagement and personal scandals forced from the throne when James was still a baby.
*Mary II co-reigned with her husband (and first cousin) William III with the understanding that if she died before him, which she did, her sister Anne would not assume the throne until his death.