TORONTO -- Same-sex parents in Ontario and others who use assisted reproduction to conceive will no longer have to adopt their own children.

The All Families Are Equal Act ensures that couples such as those who use a sperm or egg donor or a surrogate are legally recognized as parents, updating parentage laws for the first time since 1978.

Under the old rules, same-sex parents often had to go to court to get that legal recognition.

The government legislation followed a private member's bill from New Democrat Cheri DiNovo called Cy and Ruby's Law, named for the children of Jennifer Mathers McHenry and her wife Kirsti. They experienced a difficult childbirth and they realized if Jennifer had died Kirsti may not have legally been able to take the baby home.

The law, which will be in force as of Jan. 1, passed the Ontario legislature unanimously Tuesday, though nearly half of the Progressive Conservative caucus was absent for the vote.

Some of the absent members represent the more socially conservative views in the caucus, including a 19-year-old who was elected in a byelection Nov. 17 but has delayed his swearing-in until Wednesday.

The Liberals failed in a last-minute request to delay the vote to wait for Sam Oosterhoff, who says he is "100 per cent pro-life" and campaigned against the updated sex-ed curriculum. Oosterhoff could have been sworn in as early as Monday, when the new Liberal MPP elected the same day as Oosterhoff entered the legislature.

Party Leader Patrick Brown, who has been trying to brand his party as socially progressive and expected his caucus to vote in favour of the bill, denied that Oosterhoff's swearing in was delayed to avoid the vote, saying he just wants to ensure all his family and supporters can attend a party at the legislature that day.

"He can have his swearing in when he wants it," Brown said.

"Sam's having his swearing in tomorrow. I've made it clear where I stand on Bill 28 and the vast majority of our caucus was there supporting Bill 28."

But of the 29-person caucus, 12 members were absent for the vote, including several MPPs who had been in question period just minutes earlier. Brown said one had a medical appointment.

"I don't think some of the members who weren't here are the more socially conservative ones," he said. "I disagree with that assessment."

Absent members included one who fought the sex-ed curriculum, a creationist, and one who got in trouble for misogynist "jokes."

Deputy Premier Deb Matthews said it's no coincidence that Oosterhoff and others weren't there.

"I think you can read into that that they were opposed to the bill," she said.

Social conservatives fought against the bill, upset that the term "parent" is used instead of "mother and father."

Progressive Conservative Randy Hillier gave voice to some of that opposition during the last debate, but ultimately voted in favour.

"Bill 28 does more than simply update our laws," he said. "It also extends our laws into some unknown and uncharted areas with consequences unseen. It permits four -- or in some cases more than four people -- to become parents of a child. It does this while providing no explanation as to the problem this aspect of the legislation is meant to solve."

The law allows for a birth parent to enter into a "pre-conception parent agreement" with up to four people.

DiNovo said the same arguments of not having thought through the ramifications were made in opposition to same-sex marriage, and more than a decade later, "the sky has not fallen."

"Heterosexual couples that have divorced and remarried where children spend some time at one household and some time in another already have four parents," she said. "This is not a social experiment. This has been going on for as long as marriage has been going on. This is just equality we're talking about."