H.R.H. the Infanta Doña Alicia
I’m so sorry for the late answer, I completely missed this question!
I don’t think there were any protestant royals during the reformation. I know that Juana I’s daughter Isabel (Carlos I, Holy Roman Emperor’s sister), who became Queen of Denmark after her marriage to Christian II, became interested in Protestantism after her husband’s exile. Christian wanted her to hide this as it could only upset her powerful family and he needed all the help he could receive. (Fun fact, after she died there were masses held in her honor in Spain, the Netherlands and Hungary)
(And to add insult to the injury Isabel of Austria was named after her maternal grandmother Isabel, the Catholic Queen ;) )
Federico de Madrazo: La Infanta Luisa Fernanda. Luisa Fernanda, Infanta of Spain and sister of Isabella II. She married Antoine d’Orléans, Duke of Montpensier, the youngest son of Louis Philippe. During the revolution of 1868, Montpensier supported the opponents of his sister-in-law, hoping to ascend to the throne. However, he dilapidated any possibility when he fought a duel against the Infante Enrique - brother of the consort king - and killed him. Montpensier was convicted and sentenced to prison. Obviously, the relationship between the two sisters had become by then very tense.
The Spanish parliament later chose Amadeo of Savoy as the new king. Montpensier and his family were exiled, but returned in 1874.
Queen Regent Maria Cristina of Spain and daughters, infantas Maria Teresa and Maria de las Mercedes.Mids 1880s.
Wow! That woman was really beautiful (or the painter did her really beauitful).
Sofonisba Anguissola (who arrived in Spain as one of her mother’s ladies and stayed many years at court after her death so may have been partial to her) also painted a beautiful Catalina Micaela (El Prado lists this portrait as a Sánchez Coello work but acknowledges that some maintain this is Anguissola’s)
Catalina Micaela by SA:
Infanta Carlota Joaquina of Spain & Queen consort of Portugal.
Infantas Maria de las Mercedes (left) and Maria Teresa of Spain. 1900s.