Philip III of Spain (1578 - 1621). Also, as Philip II, King of Portugal, Naples, Sicily and Sardinia and Duke of Milan from 1598.
No references for this one as of yet. Just portraiture to go by, which seems to depict him with blondish hair, possibly tending to ginger. Definitely a tentative addition to the collection, but very much worth taking note of due to the unexpected number of red and fair-haired royals in the Spanish lines.