Don Juan's Dad was Holy Roman Emperor Charles V of Austria. His Mom was Barbara Blomberg, a local singer who entertained Charles with music and fun while he passed through Regensburg in 1546.
Not much more is heard in history about Barbara, but we are grateful to her for bearing John of Austria, who led the allied navies against the Ottomans at the Battle of Lepanto in 1571.
It is believed that John was conceived during a one-night-stand in this old hotel in Regensburg (yellow one on the right, a week or so ago). An historic little hook-up indeed: