Elisa B. (defendant) and Emily B. were a lesbian couple who agreed to start a family together. Using the same anonymous sperm donor, each became pregnant. Elisa gave birth to a child in November 1997. Emily gave birth to twins in March 1998. One of the twins was born with Down’s syndrome and had serious health problems. Neither woman adopted the children of the other, nor did Emily and Elisa register themselves under California’s domestic partner law. They lived and held themselves out as a family of five, however. Both women breastfed all three children and gave them the same surname: a hyphenation of Elisa’s and Emily’s. Elisa named the three children as dependents on her tax returns. Because Elisa made more money than Emily, they agreed that Elisa would support the family financially while Emily stayed at home for a few years. In November 1999, Emily and Elisa split. Elisa initially provided financial support to Emily and the twins but eventually stopped. Emily and the twins were forced to seek public assistance. The District Attorney of El Dorado County brought a lawsuit in the Superior Court (plaintiff) against Elisa for the payment of child support. The Superior Court ruled that Elisa was liable under the principle of equitable estoppel. The Court of Appeals reversed on the grounds that Elisa was not responsible under California’s version of the Uniform Parentage Act (UPA). The California Supreme Court agreed to review the decision.