A cousin of Gov. Gavin Newsom’s wife, Jennifer Siebel Newsom , is throwing his tech fortune behind two of the governor’s biggest critics. Siebel Systems founder Tom Siebel, second cousin of Siebel Newsom, gave $50,000 to San Jose Mayor Matt Mahan’s bid for California governor and another $10,000 to Republican former Fox News Host Steve Hilton. Siebel sold Siebel Systems , an enterprise software firm, to Oracle to 2006 for approximately $5.8 billion, making him a billionaire with an estimated