Leopold I entered into matrimony with Sophie, the widowed spouse of Duke Berthold III of Zähringen.

[1] Leopold was actively involved in the governance of the realm during his father's reign, often referred to as "junior margrave" in historical documents.

He embarked on an ambitious endeavor to establish new municipalities and cities, contributing to the growth and development of the region.Leopold's attention also turned towards expanding his influence into territories held by the House of Eppenstein in Carinthia.

Through diplomatic maneuvering and military campaigns, he successfully acquired key regions such as "Mark an der Mur," previously under Carinthian control.Furthermore, Leopold sought to integrate additional territories into his margraviate, including the Margrave in Ennstal and the City of Leoben.

[3] Following the passing of Leopold I of Styria in October 1129, Sophie assumed regency over Styria for an extended period due to the young age of his son Margrave Ottokar III of Stryia, who was just 4 years old at the time of Leopold's demise.