Legal Question in Wills and Trusts in California

Re: death

California does not recognize common law marriage. Unless he named her in his Will or Trust, nothing would pass to your sister. If he died intestate (without a Will), was unmarried at the time of his death, and has children, then his assets would pass to his children in equal shares.

Your sister may have a claim against the Estate if she contributed to the mortgage, improvements to the house, or the purchase of personal assets, but this would depend on the circumstances and the intent of the parties.