Since I've revived my Prince's Survival TL, I've been wondering about the younger of the D. Juan d'Austrias. Born in 1627, he sincerely seems to have entertained hopes of succeeding father dear as king of Spain if something were to have happened to Carlos II (probably the reason Mariana of Austria didn't like him). Although he seems to have made a suggestion to his father about marrying his half-sister on that man's deathbed (something that Felipe IV got up and whacked him with a cane for), and his father had spoken rather vaguely of D. Juan José marrying a Mazarinette, nothing concrete was ever decided on.
So, who would be the most likely candidates for a missus? And what might happen if the royal bastard sires a family?