The institution of marriage is on the decline in the metropolitan area of Ottawa-Gatineau, according to new census data that offers fresh insight into the complex composition of modern-day Canadian families.

The latest information from the 2011 census, released Wednesday by Statistics Canada, reveals the many different ways Canadians live together as a family unit: married, common-law, same-sex, with or without children and — tracked for the first time — in Brady Bunch-style stepfamilies.

When the census was taken in May 2011, there were 340,515 families in the census metropolitan area of Ottawa-Gatineau.

Statistics Canada defines a census family as being composed of a married or common-law couple, including those with children, or of a lone parent living with at least one child in the same household.

Married couples — those with and without children — make up 66.1 per cent of families in the Ottawa-Gatineau region. That is a decrease from the last census taken in 2006 when 67.3 per cent of couples were married. Common-law couples make up 17.4 per cent of the families, up from 2006.

Across Canada, the percentage of married couples has dropped over the last five years from 68.6 per cent to 67 per cent of all families. Couples living together without being legally married make up 16.7 per cent of all families across the country, an increase from the 2006 census when it was 15.5 per cent.

The new census data shows some other interesting details about families in the Ottawa - Gatineau region:

• Stepfamilies — defined by Statistics Canada as couples living with one or more children where at least one child is the biological or adopted child of only one of the parents — represent 6.7 per cent of all families in the Ottawa-Gatineau region. This is the first time Statistics Canada has counted stepfamilies in a census.
• The percentage of people in the Ottawa-Gatineau region who are divorced is 8.5 up from 8.2 per cent in 2006.
• A total of 0.3 per cent of children under the age of 15 live with at least one grandparent, instead of a parent.
• 16.6 per cent of families are headed by single parents: 13 per cent by single mothers and 3.6 per cent by fathers.
• There are 3,315 same-sex couples (1.2 per cent of all metro Ottawa-Gatineau couples), up from 2,425 (0.9 per cent) in 2006.
• About six per cent of households have adult children aged 25 and over still living at home.

Statistics Canada uses the term census metropolitan area to describe any area with a population of at least 100,000, where the urban core of that area has at least 50,000 people. Looking at metropolitan areas this way takes in to account the growing impact of suburban areas on Canada's largest cities.