A child can legally have three parents, Ontario's highest court ruled in a landmark decision Tuesday.

In the so-called "two-mother" ruling, the Ontario Court of Appeal said the biological mother of a five-year-old boy and her same-sex partner can both be legally recognized as mothers of the child. The boy's biological father is still recognized as his dad.

"It's not an academic issue; it's very much a practical issue," said the father's lawyer, Alf Mamo.

"If the biological parent is away, and the child gets sick and they have to go to the hospital, and the doctor wants the parent to sign a consent, there has to be the ability to do that," said Mamo.

Father would lose status if boy adopted

The boy's mother and her partner have been in a stable same-sex union since 1990. In 1999, they decided to begin a family with help from a friend, the court heard.

Both women were to be the child's primary caregivers, but believed it would be in the child's best interests for the biological father to be involved in his life.

The mother and her partner did not apply for an adoption order because, if they did so, the father would lose his status under the Child and Family Services Act, Ontario's legislation covering child protection and adoption, court heard.

"Perhaps one of the greatest fears faced by lesbian mothers is the death of the birth mother. Without a declaration of parentage or some other order, the surviving partner would be unable to make decisions for their minor child, such as critical decisions about health care."

'Gap' in laws revealed

The Appeal Court ruled that the provincial legislation dealing with issues of custody, the Children's Law Reform Act, no longer reflects current society.

"There is no doubt that the legislature did not foresee for the possibility of declarations of parentage for two women, but that is a product of the social conditions and medical knowledge at the time," they wrote.

The judges said a "gap in the legislation has been revealed," and the statute does not reflect the best interests of the child in this case.

"The act does not deal with, nor contemplate, the disadvantages that a child born into a relationship of two mothers, two fathers or as in this case two mothers and one father might suffer," the judges wrote.

The appellant's application to have the case heard was dismissed by a Superior Court justice in 2003 who said he didn't have jurisdiction to rule in the case.

With files from the Canadian Press