Legal Question in Real Estate Law in California

Rights to occupy real property are various; for example, it's generally not a trespass for a stranger to walk up a sidewalk to the front door of a house, or to park in a store's parking lot. Also, any owner of a tiny fraction of a house has the right, absent some other agreement with his co-owners, to co-occupy the entire property. A non-owning parent or child might acquire rights of sorts by virtue of family law placing a burden of care upon parent for his/her child or upon an adult child for an aging parent. I'd need a lot more facts before concluding it's OK to kick 'em out.