Quit Claim and Community Property My step-dad died without a will.

Quit Claim and Community Property
My step-dad died without a will. He & my mom had built a house on land he brought into the marriage. My mom always thought the house was community property since it was built with community property assets. However, my step-dad had to mortgage the property early in their marriage to pay off his ex-wife, and my mom was required by the lendor to sign a quit claim. Her understanding was that it was a contract with the lendor, not with her husband, and that it wouldn’t affect her interest in the house unrelated to the mortgage.

Now her lawyer is saying that quit claim (signed over 20 years ago for a small mortgage that was probably paid off over 15 years ago) means the house is not community property, even though it was built with community assets. Can this be correct? In that event, who is considered a ”child” under the intestate inheritance laws: only his biological children, or does it include his step-children?