 His father was Count William II of Weimar.He married Hadamut, the daughter of one Count Weriand, who in 1001 had received large estates in eastern Friuli and Istria, then part of the March of Verona ruled by the Carinthian dukes, from the hands of Emperor Otto III.Poppo thus inherited a claim to the Istrian peninsula and began to use the margravial title.