Complex sentence: Alexander remarried with Marie van Hoorn, daughter of Willem, Lord of Duffel, in 1410, but died without issue and the Earldom of Mar passed to the crown.
Split into simpler sentences: Alexander remarried with Marie van Hoorn, daughter of Willem, Lord of Duffel, in 1410. He died without having a legitimate male heir, and the Earldom of Mar passed to the crown.