Family law

First, your parents' "last wishes" may have some moral force with your siblings, but have no legal effect unless they expressed those wishes in a valid will.  Assuming that your parents owned the house jointly (i.e. either as joint tenants or tenants by the entirety, which is usual with married couples) so that the survivor of the two of them would inherit the house upon the other's death, and owned it  outright,( i.e. with no one else on title, the house was not owned by a trust, etc.) and that there was no will. and that all of their children are living, each of their surviving children (assuming they had no children of other relationships) would inherit 1/5 of the house.  This means that you own 1/5 of the house and that your siblings cannot do anything with it without your consent (or a court order).  However, unless California law is different than the law in the states in which I practice, that doesn't give you the right to live there rent free.  As you can see, there are some complex issues here, and you should probbably consult a California lawyer.