Complex sentence: From 1580-1640, Portugal was joined with Spain as part of the Iberian Union led by Spanish monarchs, Sancho III of Navarre and Alfonso VII of León and Castile both took the title "Imperator totius Hispaniae", meaning "Emperor of All Spain".
Split into simpler sentences: From 1580-1640, Portugal was joined with Spain as part of the Iberian Union. The Iberian Union was led by Spanish monarchs, Sancho III of Navarre and Alfonso VII of León and Castile both took the title "Imperator totius Hispaniae", meaning "Emperor of All Spain".