P and D entered into a lesbian relationship in 1993. They introduced each other to friends as their 'partner,' exchanged rings, opened a joint bank account, and believed they were in a committed relationship. They both wished to give birth. Because D earned more than twice as much money as P, they decided that P 'would be the stay-at-home mother' and D' would be the primary breadwinner for the family.' At a sperm bank, they chose a donor they both would use so the children would 'be biological brothers and sisters.' Both become pregnant. They attended childbirth classes together so that each could act as a 'coach' for the other during birth, including cutting the children's umbilical cords. D gave birth to Chance in November 1997, and P gave birth to Ry and Kaia prematurely in March 1998. Ry had medical problems; he suffered from Down's syndrome and required heart surgery. They jointly selected the children's names, joining their surnames with a hyphen to form the children's surname. They each breastfed all of the children. D claimed all three children as her dependents on her tax returns and obtained a life insurance policy on herself naming D as the beneficiary so that if 'anything happened' to her, all three children would be 'cared for.' D believed the children would be considered both of their children. D treated all of the children as hers and told a prospective employer that she had triplets. P and D identified themselves as coparents of Ry at an organization arranging care for his Down's syndrome. They consulted an attorney regarding adopting 'each other's child,' but never did so. Nor did they register as domestic partners or execute a written agreement concerning the children. They separated in November 1999. D promised to support P and the twins 'as much as I possibly could' and initially paid the mortgage payments of approximately $1,500 per month on the house in which D and the twins continued to live, as well as other expenses. D applied for aid. After the house was sold, D paid P $1,000 a month. In early 2001, D stated she lost her position as a full-time employee and told P she no longer could support her and the twins. At the time of trial, D was earning $95,000 a year. The court found that D was obligated to support the twins under the doctrine of equitable estoppel. D was subsequently ordered to pay child support in the amount of $907.50 per child for a total of $1815 per month. D petitioned for a writ of mandate, and the court directed the superior court to vacate its order and dismiss the action, concluding that D had no obligation to pay child support because she was not a parent of the twins within the meaning of the Uniform Parentage Act. This appeal resulted.