Complex sentence: In 1391, at the age of twelve, Joan married Robert Ferrers, 5th Baron Boteler of Wem at Beaufort-en-Vallée, Anjou.
Split into simpler sentences: In 1391, at the age of twelve, Joan married Robert Ferrers, 5th Baron Boteler of Wem. Robert De Ferrers married Joan Beaufort in 1391 at Beaufort-en-Vallée, Anjou.