I feel like I read somewhere that, in an attempt to make sure Ferdinand Magellan returned to Spain, King Charles held his wife and kids hostage (or at least kept them in the area) until he returned from circumnavigating the world. Is there any truth to this?
Magellan's wife and children weren't hostages for use as insurance or blackmail. The King of Portugal was attempting to kill Magellan. He destroyed the family castle in Portugal, sent assassins after Magellan and even sent ships after the fleet to stop the voyage. The location of Magellan's wife, Beatriz Barbosa, during the voyage is not clear from the couple's correspondence but it seems most likely to be with her father at their family home, not at court under the watchful eye of the Spanish king. Her father, Diego Barbosa frequented the king's court, so of course it seems possible that her father was helping to keep an eye on her safety and that of their young son for the king.