To hear the politicians tell it, there's a typical Canadian family out there that is the justification for many an election promise, tax break or new policy.

It's a central theme of every party platform and speech. Last spring, Stephen Harper was "here for hard-working families," the late Jack Layton offered "to give families a break" and Liberal hopeful Michael Ignatieff touted "your family, your future, your Canada."

On Wednesday, Statistics Canada's third tranche of data from the 2011 census — this one focused on families and their living arrangements — will make it clear that in this country, "family" can mean almost anything at all.

For the data collectors, there is no such thing as a generic Canadian family. Rather, there are at least eight different 'family' categories, some so complex that officials had to develop a flow chart just to start explaining what they're talking about.

At its most basic level, Statistics Canada defines a family as a couple — with or without children, married or common-law — or a lone parent with at least one child in the same house.

In other words, it takes at least two people to make a family. Beyond that, almost anything goes.

There are skip-generation families, intact families, simple step families, complex step families, opposite-sex families and same-sex families.

Tracking foster children

The census will go further than ever before in counting and describing stepfamilies and how their households are set up.

And for the first time, the census will be tracking the number of foster children — to the delight of child welfare researchers.

"The fact that it's national data — data being collected through a national statistical organization — helps to bring focus on the question of foster care and foster children, at a national level," said Nico Trocme, director for McGill University's Centre for Research on Children and Families.

"Foster children are one of the most vulnerable groups in Canada. We need to be shining a light on them more often, rather than less. So I'm thrilled."

For now, there remains no sure-fire way of knowing how many foster children there are in Canada, Trocme said — let alone where they are from, what their challenges are, and what kinds of supports they need.

Trocme, who has spent a career cobbling together estimates based on various strains of provincial data, isn't sure the census will tell him exactly what he needs to know to take his research further. But he said the new data will establish a baseline that will propel solid work in the coming years.

Blended families

Wednesday's data will also reveal just how commonplace divorce and so-called blended families have become.

On the marriage front, it will show how many same-sex couples have formalized their relationships since gay marriage became legal in Canada.

As for kids, are more couples having them? Were those couples actually married? The 2006 census showed that for the first time, there were more childless couples than couples with children in Canada. Was it just a blip, or an enduring trend?

And do the kids ever leave home? Have multi-generational households become more common?

Those are questions that fascinate Nora Spinks, who heads the Vanier Institute of the Family in Ottawa.

Spinks has been handling research on all those topics, and the census will give her the data she needs to validate conclusions and update her numbers — leading to more relevant research in the months to come.

Spinks said she's particularly keen to see who is living with whom inside Canadian households. She suspects that with an aging population, she will see evidence of children living with grandparents and even great-grandparents as families look for efficient caregiving arrangements that work for multiple generations.

Like many social scientists, Spinks has been watching the trend of young adults staying at home with parents, or moving back in after a time away. The census data will clarify how entrenched that pattern is, she said.

"Are young people truly returning home in large numbers, and to what extent? Is it a passing phenomenon?" she pondered. "When they return home, are they starting families?"

The census should also detail how seniors are living: in group homes, with relatives, or alone.

But much of the focus on the census analysis will be on blended families. For the first time, Statistics Canada has counted and quantified stepfamilies, delving into the dynamics of re-marriage.

The data will be of more than just passing interest, said Spinks. Armed with solid data about how old most children are when their families split up or reformulate, social scientists will be better able to design supports and counselling programs.

"There may be different kinds of supports needed if it's mainly pre-schoolers or adolescents," Spinks said.

"It will gives us some insights into the kinds of stresses families face today."