Otto von Habsburg, who witnessed the disintegration of the empire his family ruled for centuries and emerged from its ashes as an early champion of a united and democratic Europe, died July 4 at 98. Dr. von Habsburg, the oldest son of Austria-Hungary’s last emperor, died of undisclosed causes at his villa in Poecking in southern Germany, where he had lived since the 1950s. As the head of one of Europe’s oldest and most prominent families, Dr.