In 1988, Ernst August unsuccessfully claimed custody of his infant nephew Otto Heinrich, son of his younger brother, Prince Ludwig Rudolph of Hanover. The infant's mother, Isabella von Thurn und Valsássina-Como-Vercelli, died of cocaine overdose on 28 November 1988. Ludwig Rudolph placed a call to his brother in London, imploring him to take care of the couple's 10-month-old son, and shortly afterwards died by suicide. Custody of Otto Heinrich was eventually awarded, contrary to the expressed wishes of Ludwig Rudolph as the surviving parent and Ernst August's legal efforts, to the child's maternal grandparents, Count Ariprand (1925–1996) and Countess Maria von Thurn und Valsassina-Como-Vercelli (born 1929), to be raised at their family seat, Bleiburg Castle in southern Austria.