Gavin Newsom wasn’t born rich, but he was born connected — and those alliances have paid handsome dividends throughout his career. A coterie of San Francisco’s wealthiest families has backed him at every step of his political rise, which in November could lead next to his election as governor of California. San Francisco society’s “first families” — whose names grace museum galleries, charity ball invitations and hospital wards — settled on Newsom, 50, as their favored candidate two decades ago, said Willie Brown, former state Assembly speaker and former mayor of the city.