Question: The father of Pietro de' Medici was the Duke of Florence between what years?
Related documents: [0]  [DOC] Don Pietro de' Medici (3 June 1554 – 25 April 1604) was the youngest son of Cosimo I de' Medici, Grand Duke of Tuscany and Eleonora di Toledo. [END] 
[1]  [DOC] Cosimo I de' Medici (12 June 1519 – 21 April 1574) was the second Duke of Florence from 1537 until 1569, when he became the first Grand Duke of Tuscany. [END] 
Answer: 
1537 until 1569
1537 until 1569