Legal Question in Wills and Trusts in California

If the will, if there is a will, or your father's trust if he has one, does not have a "spendthrift clause" prohibiting voluntary and involuntary assignments of your interest in your father's estate, then you could, after your father's death, assign your beneficial interest in this property to your sister.

Or, if the probate will be over soon, then once it's over you could quitclaim your interest in the home to your sister.

However, if your father is alive, it's best that he amend his will or trust to leave more of the property to your sister, as that way there's no sibling to sibling transfer after your father's death that would subject this 1/5 portion of the property to a reassessment under Prop 13. If that's not possible, it may be possible for you to disclaim your interest in the home, but you would have to review the matter with a trusts and estates attorney first, and you cannot disclaim an asset more than 9 months after the date of death.

or you can just disclaim the inheritance in probate.