Common law marriage has long been abolished in California. So generally, unless an unmarried couple who lived together register as domestic partners, they acquire no rights that are granted to married couples or registered domestic partners. However, the partner may have remedy in an ordinary civil action, instead of the family court, if they would want to stake claim at properties owned by the deceased. Talk to an attorney for more information on how to protect your interest and your mother’s estate from those who might possibly take advantage.