Original: By the end of the battle, de Montfort's forces capture both King Henry and his son, future King Edward I, making de Montfort the "uncrowned king of England" for 15 months before Edward escapes captivity and recaptures the throne.
Simplified: By the end of the battle, de Montfort's forces capture both King Henry and his brother, future King Edward I, making de Montfort the "uncrowned king of England" for 15 months before Edward escapes captivity and recaptures the throne.