In 2009, 7.8 million children lived with at least one grandparent, a 64 percent increase since 1991 when 4.7 million children lived with a grandparent, according to a report from the U.S. Census Bureau.

Among children living with a grandparent, 76 percent also were living with at least one parent in 2009, not statistically different from the 77 percent who lived with at least one parent in 1991.

“The people with whom children live affect their well-being,” Rose Kreider, a family demographer with the U.S. Census Bureau, said in a statement. “These statistics give us a lot of detail about the number of parents children live with, as well as whether they live with siblings, grandparents or other relatives.”

These statistics come from the household relationship module of the Survey of Income and Program Participation collected in 2009 and published in the report Living Arrangements of Children: 2009.

In 1991, 5 percent of white, 15 percent of black and 12 percent of Hispanic children lived with at least one grandparent. By 2009, 9 percent of white, 17 percent of black and 14 percent of Hispanic children lived with at least one grandparent, a significant change for white children but not for black or Hispanic children.

Many children who do not live with a parent live with a grandparent. More than half of the children living with no parents were living with grandparents. Percentages for black children (64 percent) and non-Hispanic white children (55 percent) did not differ from Hispanic children (61 percent), but the percentage of Asian children living with no parents who lived with grandparents was lower, at 35 percent.

In 2009, 69 percent of the 74.1 million children under 18 lived with two parents. Four percent (2.9 million) of all children lived with both a mother and father who were not married to each other.

Between 1991 and 2009, children living with only their mother increased from 21 percent to 24 percent.

The percentage of children living with their mother without a father present varied widely among race and origin groups in 2009, from 8 percent for Asian children to 50 percent for black children. Seventeen percent of non-Hispanic white children and 26 percent of Hispanic children also lived with their mother only.

Seven percent of all children lived with an unmarried parent who was cohabiting. The percentage of all children who lived with a cohabiting parent ranged from 2 percent for Asian children to 9 percent for Hispanic children. Falling between these were non-Hispanic white children (6 percent) and black children (7 percent), not different from each other or the percentage for all children.

Overall, 16 percent of children lived with a stepparent, stepsibling or half sibling. Thirteen percent of children living with one parent and 18 percent of children living with two parents lived in these blended families.