Peter was born in Belgrade on 11 July 1844, the fifth of Prince Alexander Karađorđević and his consort Persida Nenadović's ten children. He was the grandson of Karađorđe, the leader of the First Serbian Uprising (1804–1813) and the founder of the Karađorđević dynasty. Peter was not born in the Royal Court, which was undergoing renovations at the time, but at the home of merchant Miša Anastasijević. His birth was not met with much celebration because he was his parents' third son and his older brother Svetozar was the heir to the throne. His parents' oldest son, Aleksa, had died three years prior to Peter's birth, aged five, at which point Svetozar became heir. Peter did not become heir until Svetozar's death in 1847 at the age of six. Besides Belgrade, Peter spent much of his childhood in the town of Topola, from where the Karađorđević dynasty originated. He received his elementary education in Belgrade.