Mercedes married in Madrid on 14 February 1901, her second cousin, Prince Carlos of Bourbon-Two Sicilies, a nephew of the King of the then-defunct Kingdom of the Two Sicilies, who was elevated to the rank of Infante of Spain. The marriage was highly controversial due to her father-in-law's ties with the Carlists. She died three years later from complication while giving birth to her third child.
