The title of Infante/Infanta is reserved for the children of the monarch and the children of the Prince(ss) of Asturias. Other Infantes can be created by the monarch...Queen Isabel II, for example, made all her Montpensier nephews and nieces Intantes(as).
King Juan Carlos has only given the title of Infante to his first cousin, Prince Carlos of Bourbon-Two Sicilies. The next Infante(a) will be the child of the Prince an Princess of Asturias.
Baby Bee's husband was an Infante Alfonso de Orleans was one because so willed it Queen Regent Maria Cristina...but his own children were only Princes. Baby Bee and Alfonso had three sons: Alvaro, Alonso and Ataulfo. Alvaro married morganatically the very wealthy Carla Parodi Delfino, Alonso died in action during the civil war and Ataulfo was gay. Hence only Alvaro had descendants and since these were with a wife of unequal rank, then technically they were not royal children.
Arturo Beéche