Simon de Montfort, the 6th Earl of Leicester, in April 1263 called fellow barons to meet him at Oxford where they discussed rebellion against Henry's policies. This resulted in the Second Barons War (referenced here).
Richard stayed with his brother in opposing the Barons; possibly he thought some day he could still be King of England and didn't want the barons to have more power. Richard was captured (after running away and hiding in a windmill) along with Henry at the Battle of Lewes.
Believe it or not, in Germany they felt that Richard could not fulfill his duties as King of the Romans and tried to slip Conradin onto the throne. Pope Clement IV and Ottokar II of Bohemia (who had voted for Richard in the first place) blocked the usurpation. Once Richard got out of captivity he made Ottokar his administrator for everything on the right bank of the Rhine.
Richard had a son by his first wife, Isabel Marshal, Henry of Almain, the only child of theirs that lived to adulthood. At the Battle of Evesham, Henry de Montfort was killed by the royalist forces. Henry's sons, Simon the younger and Guy de Montfort, killed Henry of Almain while Henry was attending services at the church of San Silvestro in Viterbo (Italy) on 13 March 1271, as revenge for the death of their father.
This was sadder (in a sense), because the men involved were cousins. Richard and King Henry's sister, Eleanor Plantagenet, married Simon de Montfort (although against the wishes of Richard) in 1224.
By the time of Richard's captivity by Simon, his wife Sanchia had died. During a time in Germany while he helped to liberate Dietrich I, Count of Falkenburg, during which he fell in love with Dietrich's 15-year-old daughter Beatrice (Richard was 61). They married on 16 June 1269 and he brought her back to England, never again returning to Germany.
Richard died 2 April 1272 after only two years of marriage. He was buried next to Sanchia and Henry of Almain at Hailes Abbey, which Richard founded.
It's time, however, actually to look into the man that started so much trouble in England, Simon de Montfort.
