King Fernando VII first married Marie Antonietta of Naples, but the marriage did not produce an heir, so Isabel de Bragança was wife number two.
According to her Wikipedia article, "It is due to Queen Maria Isabel's dedication and affection for the art world that she managed to gather many treasures from the past and create a royal museum, which would end up being the beginnings of the Museo Nacional del Prado. It opened on 19 November 1819, a year after the Queen's death.”
She died without bearing an heir, so King Fernando VII went on to marry Maria Josefa de Sajonia.
