Canadian families are smaller, increasingly urban and made up of an ever-broadening mix of relationships.

The 2011 census confirms what Canadians see in their day-to-day lives: married couples are still the predominant family structure, but it is a category that continues a decades-long decline.

In its place, a growing number of Canadians are living in common-law relationships, single-parent families or living alone. For the first time, there are now more one-person households than couple households with children.

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Wednesday's release from Statistics Canada is the third of four announcements based on the 2011 mandatory short form census. In 2013, Statistics Canada will release information from the voluntary National Household Survey, which replaced the mandatory long form census.

The latest round of data from the short-form census, released Wednesday morning, focuses on the living arrangements of Canadians. The information is extremely valuable to federal, provincial and municipal governments as it shows which parts of Canada have rising seniors populations and which parts of the country – as well as which parts of Canadian cities – have more young families.

The data can be used to guide decisions on where to build new schools and parks because it shows which parts of the country have more young families. The data can also inform broader national questions about immigration, health care and labour mobility.

Wednesday's release includes closer looks at the living arrangements of Canadians aged 20-29, as well as Canadian seniors. For young adults, about four in 10 live with their parents, which is largely unchanged from 2006. For seniors, Statistics Canada found that while women were twice as likely to live alone than men, the percentage of female seniors living alone is on the decline.

Anne Milan, a sociologist with Statistics Canada, says this is primarily because men are living longer than they used to. "One of the results of that is seniors can stay in a couple for a longer period of time," she said in an interview.

Wednesday's census release marks the first time that the census has recorded a five-year period in which same-sex marriage has been legal in Canada. Parliament approved same-sex marriage legislation in 2005.The census found 64,575 same sex couple families in Canada, up from 45,345 in 2006.

Of those, 21,015 were same-sex married couples and 43,560 were same-sex common law couples. As a percentage, the share of married same sex couples is 32.5 per cent, up from 16.5 per cent in 2006. Same-sex couples were more likely to be male (54.5 per cent) than female (45.5 per cent) in 2011.

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Same-sex families in Canada are less likely (at 9.4 per cent) to have children at home than opposite-sex couples (47.2 per cent), though same-sex female couples are more likely to have children than male same-sex couples. Female couples made up 80.3 per cent of same-sex couples with children.

The 2011 census also marks the first time that step-families were recorded. Families in which all children are the biological or adopted children of both parents are called "intact" families by Statistics Canada and account for 87.7 per cent of all families. Step-families account for 12.6 per cent of Canadian families.

Overall, Canadian families are getting smaller as the fertility rate declines and the number of lone-parent families increases. The average number of children per family decreased from 2.7 in 1961 to 1.9 in 2011.