Dr. Siebert is the president of the California Institute of Technology. Judging from his acts in the show, he seems to be responsible for getting funding for the university, and supervises how the funding are used. He is married and has a teenage daughter, and his family owns several dogs; his mother is probably deceased. In "The Rothman Disintegration" (S5E17), when Sheldon and Kripke were fighting over who would get Rothman's office they asked Siebert, who was urinating, to decide who gets the office he said he had to let them work it out, as he couldn't care less who inherits said office.