Even as the definition of family in America expands and shifts, California courts are trying to keep pace by redefining whom the law regards as parents.

Judges have moved beyond traditional notions of biology and adoption and have assigned parental rights to adults with no genetic or legal ties to kids.

In a recent Sacramento case, an appeals court said a woman who never adopted her ex-girlfriend's children was nevertheless their parent because she acted like one – providing for them financially, cleaning up after them when they got sick, and volunteering at their school.

"We're redefining what constitutes a family," said McGeorge School of Law Professor Larry Levine, an expert on sexual orientation and the law. "It's a whole new way of thinking about this."

In the Dec. 9 ruling, the Sacramento-based 3rd District Court of Appeal said the woman had a good reason for not adopting the children.

She was a colonel in the Air Force Reserve and was afraid of being expelled from the military if she violated the "don't ask, don't tell" policy in force at the time. The controversial policy, which began in 1993 and ended in September, barred openly gay men or lesbians from serving in the military.

Had the woman been open about her sexual orientation by forming a domestic partnership or adopting her girlfriend's children, it might have ended her military career.

The court referred to the woman and her former partner only by their initials: S.Y. and S.B. The Bee agreed to do the same to protect the privacy of the children.

"It was never even something we discussed about me participating in the adoption or formalizing the relationship," S.Y. said in an interview. "It was just a given because of 'don't ask, don't tell.' When it's something you can't do, you don't go there."

S.B. declined through her attorney to comment on the case.

Her lawyer, Elizabeth Niemi, said S.B. always planned to be the children's sole parent. She hadn't wanted S.Y. to jointly adopt the children, and S.Y. acknowledged that was true in trial testimony, she said.

"Neither party ever intended for S.Y. to have parental rights or obligations," Niemi said.

But the court said the adoptive mother's intentions weren't the deciding factor.

"Whether S.B intended for S.Y. to obtain legal rights with respect to the children is irrelevant where, as here, S.B. allowed and encouraged S.Y. to function as the children's second parent from birth, and S.Y. openly embraced the rights and obligations of being a parent," wrote acting Presiding Justice Cole Blease for the unanimous panel.

The three justices on the panel – including Justice George Nicholson and Justice Andrea Lynn Hoch – upheld a ruling by Sacramento Superior Court Judge Helena Gweon.

Experts said the case continues a trend in which courts have ruled that adults who aren't biological or adoptive parents can still be assigned parental rights and responsibilities.

The purpose: to promote the well-being of children and ensure their financial support, Levine said.

"The state has a great interest in having those who want the benefits of parenthood to take on the responsibilities and obligations that go with parenthood," he said. "That's true for straight and gay couples."

The string of cases that led to this month's ruling in S.Y. v. S.B. included the California Supreme Court's 2002 decision in a case involving a boy identified as Nicholas H. In that case, the court granted custody to a woman's former live-in boyfriend, who admitted he was not the boy's biological father but had acted as his father since birth.

The biological father was nowhere to be found.

Traditionally, adults not related by blood or adoption would have been deemed "legal strangers" to children, but things have changed, said Courtney Joslin, a professor at the UC Davis School of Law, who specializes in family law and sexual orientation and the law.

In the recent case, "the court says you have to look at the reality of families' lives, and the most important inquiry is whether a person is actually functioning as a parent."

Deborah Wald, the lawyer who argued the case for S.Y. at the appellate level, said the decision was part of "a sea change that started with In re Nicholas H."

"What we've seen is that the courts are starting to look at parentage issues from a child's perspective, which is a very big shift. Before, children were treated more like property.

"Now the courts are starting to ask, 'Who do these children think their parents are?' It's a child-centered approach that relies on looking at behavior. Courts aren't willing to take children away from people whom they rely upon."

Niemi, the lawyer for S.B., took away a different lesson from the case.

"If you are a single parent, and there's not another parent somewhere," she said, "you have to be careful about who you allow to have a relationship with your kids."

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