Philip of Swabia (1177-1208), German king and duke of Swabia, the rival of the emperor Otto IV, was the fifth and youngest son of the emperor Frederick I and Beatrix, daughter of Renaud III, count of Burgundy, and consequently brother of the emperor Henry VI. He entered the clergy, was made provost of Aix-la-Chapelle, and in 1190 or 1191 was chosen bishop of Würzburg. Having accompanied his brother Henry to Italy in 1191, Philip forsook his ecclesiastical calling, and, travelling again to Italy, was made duke of Tuscany in 1195 and received an extensive grant of lands. In 1196 he became duke of Swabia, on the death of his brother Conrad; and in May 1197 he married Irene, daughter of the eastern emperor, Isaac II, and widow of Roger III, Titular King of Sicily, a lady who is described by Walther von der Vogelweide as " the rose without a thorn, the dove without guile."

Philip of Swabia married Irene Angelina, daughter of Isaac II Angelus on May 25, 1197. Their four daughters were:
• Beatrice of Hohenstaufen (1198-1212), married Otto IV, Holy Roman Emperor
• Cunigunde of Hohenstaufen (1200-1248), married King Wenceslaus I, King of Bohemia
• Mary of Hohenstaufen (1201-1235), married Henry II, Duke of Brabant
• Elizabeth of Hohenstaufen (1203-1235), married King Ferdinand III of Castile