sentences:  Conrad finally submitted in 1135; the next year he joined the emperor on his Italian campaign and married Gertrude.The matrimonial alliance between the House of Hohenstaufen and the Counts of Sulzbach led to close relations between the two families; when in Gertrude's brother Count Gebhard III died, the line became extinct, leaving the Hohenstaufen emperor Frederick I Barbarossa (Gertrude's nephew by marriage) as his sole heir.After Emperor Lothair II died in 1137, Gertrude's husband Conrad finally was elected King of the Romans on 7 March 1138, though he had to ward off the claims raised by the rivalling Welf duke Henry X of Bavaria and his sons Henry the Lion and Welf VI.