Michael Tilson Thomas and Joshua Mark Robison, partners since 38 years, were married last Sunday at the home of former San Francisco Symphony board President Nancy Bechtle. According to an article published by SF Gate, the vows were administered by state Sen. Mark Leno. MTT, who will turn 70 in December, is marking his 20th anniversary this year as Music Director of the San Francisco Symphony; Robison, 68, is his manager.