Louis XIV, Child King of France
Louis XIV (1638-1715) was one of the longest reigning monarchs in history. This is in part because he lived to an advanced age, surviving both his sons and his grandson, to be succeeded by his great-grandson. It is also in part because he came to power at the age of 5, in 1643, just as the Congress of Westphalia was beginning. As an adult, Louis became the symbol of absolutism, strengthening the power and prestige of central government in France while turning France into the recognized greatest power in Europe. That was all far in the future, however, when he succeeded his father Louis XIII in 1643. He reigned, but rulership was in the hands of a regency council headed nominally by his mother, but soon dominated by Cardinal Mazarin. Louis performed a largely ceremonial role until long after the Peace of Westphalia.
There is an embarrassment of riches when it comes to biographies of the Sun King, even in English. Here are just some of the most recent.
King of the World: The Life of Louis XIV (2019) by Philip Mansel
Louis XIV (2018) by Olivier Bernier
Louis XIV: The Power and the Glory (2019) by Josephine Wilkinson