Will a quitclaim deed in which an individual who owns California property adds her brother to the title trigger a tax?

I do not think there is an exemption in California for siblings. Between parent and child or Grandparent and child there is an exemption. If there is no exemption, the property transferred is subject to a transfer tax and a reassessment.

Yes it will. In California, adding a sibling to a real property deed will trigger a reassessment for property tax purposes. In rare instances, there may be grounds to appeal such a reassessment. For example, I had a case a few years ago where a parent died intending to leave her real property to her two children. For some reason, one child's name had been added during the parent's lifetime, while the other had not been. When the second child was added following the parent's death, a reassessment was triggered because it appears to be a transfer between siblings. The successful appeal demonstrated the intention that the transfer was to be between parent and children and that deed problems were inadvertent.