Stein was the ninth child of Karl Philipp Freiherr vom Stein, and Henriette Karoline Langwerth von Simmern, the widow of von Löw. His father was a man of stern and irritable temperament, which his far more famous son inherited, with the addition of intellectual gifts, which the father entirely lacked. The family belonged to the order of imperial knights of the Holy Roman Empire, who occupied a middle position between sovereign princes and subjects of the empire. They owned their own domains and owed allegiance only to the emperor but had no votes for the Diet.