OTTAWA - The nuclear family is no longer the norm in Canada.

The mom-pop-and-three-kids-under-one-roof model that typified Canadian households of 50 years ago has morphed into a complex and diverse web of family ties involving living alone, re-marriage, stepchildren, empty-nesters and multiple generations sharing a home.

Statistics Canada has released the third tranche of new data from its 2011 census, this time portraying the changes in Canadian families and living arrangements over five decades.

Married couples are in a long-term decline, single parenting has risen persistently, and families have gradually shrunk. The average family was 3.9 people in 1961, when the baby boom was in full swing. Now, it's 2.9.

"We do see more complexity and definitely more diversity in families," said Statistics Canada demographer Anne Milan.

For the first time, Statistics Canada says there are more people living alone in Canada than there are couples with children. One-person households now make up 27.6 per cent of all homes, a three-fold increase since 1961 that is especially notable in Quebec.

Meanwhile, couples with children have continued their decline, down to 26.5 per cent of all households, from 28.5 per cent in 2006.

Just 10 years ago, couples with children under 24 years old made up 43.6 per cent of all families (not including one-person households) — by far the most typical kind of family.

Now, parents with children make up just 39.2 per cent of families, and a rising proportion of those parents are not officially married. The number of common-law couples surged almost 14 per cent between 2006 and 2011.

For the first time in 2011, Statistics Canada also measured the number of stepfamilies in the country, showing that now one in 10 children lives in some sort of reconstituted arrangement.

"The modern family is changing, and I think it's a wonderful thing," said Shannon Kennedy, an Ottawa-based wedding planner who finds herself on the front lines of fluctuating living arrangements on a daily basis. "The rules of a nuclear family just don't apply any more."

In 2011, the most typical family was a couple with no children, continuing a pattern spotted in 2006. Statistics Canada found that 44.5 per cent of families have no kids at home, partly reflecting the aging of the baby-boomer bulge, the leading edge of which has started turning 65.

Overall, there were 9.4 million families in Canada in 2011, a 5.5 per cent increase from 2006.

Despite a growing population overall, the number of married couples declined outright by 132,715 over the past decade.

Lone-parent families and multiple-family households, on the other hand, were on the rise. Single parents increased by 8.0 per cent from 2006, and more of those parents were fathers — although eight out of 10 lone parents were still mothers.

Same-sex couples were also on a steep incline, up 42.4 per cent from 2006. About half of these couples were married, while the rest were common-law. Still, same-sex couples only made up 0.8 per cent of all couples in 2011.

And for the first time, Statistics Canada zeroed in on children living in untraditional arrangements.

In Canada's first-ever national count of foster children, the agency revealed that there were 29,590 of them under the age of 14 in 2011, with the highest predominance in Manitoba, where there is a high First Nations population. Overall, 29 per cent of the country's foster children were younger than 5, and 30 per cent were between 5 and 9 years old.

More than 17,000 households are involved in taking care of foster children, and more than half of those households had taken in at least two kids.

The pure numbers are only a start in figuring out how best to support some of the most vulnerable children in Canada, researchers say. But now that they are armed with better data, social scientists will be better able to determine the needs of foster children.

"For 10 years, I've wanted to track this," said John Dunn, a former foster child who now advocates on their behalf.

What he needs to get a full picture is more data on how much money is flowing into the household — information that won't come until next August.

The census-takers also found that about one in 10 children under the age of 14 lived in some sort of stepfamily.

But such families are so complex that Statistics Canada had to include several diagrams with its census documents in order to better explain where those children came from.

Of the 3.7 million couple-families with children, 87.4 per cent are considered "intact," with all the kids counted as the offspring of both parents.

About 12.6 per cent were considered stepfamilies. Of those, 7.4 per cent were considered "simple" stepfamilies, in which all children are directly related to just one of the spouses.

The rest of the stepfamilies are considered "complex." More than half of them had three or more children.

Stepfamilies were most common in Quebec, and least common in Ontario. By city, stepfamilies were most common in Trois-Rivieres, Quebec, and least common in Toronto and Vancouver.

The wide variety of family ties is throwing wedding-planner Kennedy for a loop. Emily Post, the guru of etiquette for most of the 20th century, is no longer of much help, she said.

"You don't necessarily have two families. In some cases, you have four families coming together at a wedding."

She looks to the processional in order to incorporate divergent family demands. Any number of people can be included in the walking up the aisle, even forming a "relay" with one parent handing off the bride to a second or third parent halfway to the altar.

"Any scenario where you get more than one mom involved, you have to kind of juggle that," Kennedy said with a chuckle.

"The best thing about modern weddings is, there are no rules."