Legal Question in Real Estate Law in California

It depends upon how your sister and you hold title. If you own the home as joint tenants, when one of you passes away, the other becomes the sole owner. This is automatic and whether you have a will (or trust) or not, and what it says, is immaterial.

On the other hand, if your sister and you hold title as tenants in common, the ownership interest of whichever dies first will be inherited according to inheritance law principles, Namely, if you don't have a will or trust, or the home isn't mentioned directly or indirectly, the heirs will be determined by the laws of intestate succession, but if you do have a will or trust, the heirs will be determined by what the will or trust says.

Now, the mere failure to mention the home in your will might not mean there's nothing in the will that directs who inherits the home. Most wills have some kind of catchall provision that allocates "all other" property to someone or other. For this reason, I recommend that you get out your will and see what it says about miscellaneous or catchall or unlisted or all other property you own at the time of your death. Then, if the indicated handling isn't what you'd want, see your lawyer and have a codicil drawn up and signed.

It depends on how you and your sister hold title, how the will handles gifts that aren't specifically named, and who your heirs would be when you died.