Just reading Wiki (obviously the cornerstone of truth) and was it really his brother or half-brother?
Schwarzenegger was born in Thal, Austria, a small village bordering the Styrian capital Graz, and was christened Arnold Alois Schwarzenegger.[5] His parents were the local police chief Gustav Schwarzenegger (1907 – 1972), and his wife, Aurelia Jadrny (1922 – 1998). They were married on October 20, 1945 – Gustav was 38, and Aurelia was a 23-year-old widow with a son named Meinhard.