Legal Question in Real Estate Law in California

Any number of people can jointly own any piece of real property, although beyond a certain number it would begin to look like the interests were securities and you'd probably have to form a REIT. The two most common forms of ownership that would apply to a brother and sister are "tenants in common" and "joint tenants." If you and a sibling are considering acquiring property together, you should spend a couple of hundred dollars for face-time with a real estate attorney to review your reasons for buying together, your expectations, and help you with structuring the co-ownership. It will save a lot of potential family grief down the line.