From the Post archives, June 1969: Six youngsters who only recently met line up outside a Los Angeles courtroom to await approval of contracts calling for them to play brothers and sisters on a new television series. The series, called "The Brady Bunch," is about a widower with three boys who marries a widow with three girls. (ASSOCIATED PRESS)

Northern Virginia is a bastion of the nuclear family, but not all places are equally so.

Loudoun County, for example, has a higher percentage of nuclear families than any other county in the state. Arlington County and Alexandria are among the lowest, though they rate high on the proportion of people living alone.

Census statistics released Thursday help explain Loudoun County’s premier position as the hub of family life. It’s one of the few places in the state where the percentage of households with children under 18 rose over the past decade, from 43 percent to 46 percent. Four in 10 households are made up of married couples with children. Looked at another way, four in five children in the county live with their married father and mother, while just 12 percent live with a single parent.

The county has scrambled to keep up with a student population that has doubled in each of the past two decades. Last year, about 63,000 students attended Loudoun public schools, a number expected to swell to 66,000 this school year. In the past decade alone, the school district opened 29 schools, for a total of 80; in some school years, it opened as many as five schools. It currently has two schools under construction, and voters will be asked to vote this fall on a $170 million bond issue to fund the construction of four more, all in the Ashburn area.

“We add 3,000 students every year, with no end in sight,” said schools spokesman Wayde Bayrd.

Four other Northern Virginia counties are among the six counties in the state with the highest percentage of nuclear families — Stafford at about 33 percent, Prince William at 32 percent, Spotsylvania with 29 percent and Fairfax with 28 percent. In contrast, Arlington County, with 15 percent of all households being married couples with children, and Alexandria, with 13 percent nuclear families, are clustered near the bottom.

Even within counties, some places stand apart.

Nuclear families make up 53 percent of the households in South Riding in Loudoun County and the Linton Hall area of Prince William County. In Fairfax County, the hubs of traditional families include the Franklin Farm area of Herndon, at 44 percent, and the area around Wolf Trap in Vienna, at 41 percent.

At the other end of the spectrum, 43 percent of households in Alexandria are live-alones, as are 41 percent of the households in both Arlington County and the Tysons’s Corner area of Fairfax County.

Couples who are married but don’t have children are abundant in lots of places. They make up a third or more of the households in Buckhall and Montclair in Prince William, and in a multitude of areas around Fairfax County — Burke, Fort Hunt, Franklin Farm, McLean and Wolf Trap.

— Carol Morello