Strangely enough, both Aileen and Alison claim that they were not particularly close growing up. "When we were little, she terrorized me," says Aileen. They spent their childhood in Cleveland with their older brother, John, and their parents, Anna and Ian Hunter. "But Alison went away to college, and we started to get closer." In June 1994, as Aileen was finishing the interior-design program at the University of Cincinnati, Alison, then 28 and pursuing a marketing career in Chicago, found herself in desperate need of a roommate. So she drove to Aileen's graduation in a U-Haul. "I made her move here," the older sister jokes. "I didn't give her a choice. I moved all her things back to Chicago."

Their marriages would follow — five weeks apart in the summer of 1995 — but they would be overshadowed by their mother's declining health due to breast cancer. Anna Hunter died in the spring of 1996, on the day before her 57th birthday, but not before she knew that her elder daughter was pregnant. She predicted — accurately — that the baby would be a girl. By the end of the 90s, the sisters were both working (Aileen as a design sales representative for a furniture company), living half a mile apart in downtown Chicago, and sharing a nanny for Anna and Hunter. They'd speak vaguely about moving to the suburbs, but when Aileen and Neil had a chance to buy a friend's house in Western Springs, they made a sudden move. Alison was shocked. "I couldn't believe she was leaving. It was devastating," she says. For two years, Alison and Peter would visit Western Springs on the weekends. When the house across the street from Aileen and Neil's came on the market in 2001, the couple made an offer.

"We'd always joked about the Webers moving out to Western Springs," says Neil. "We wanted that, but across the street was another question." Both husbands were worried that their families might merge. "I wanted to make sure that when the Pendletons wanted to do something, we could do it," says Neil. "We wouldn't have to invite the Webers, and vice versa." Once they had cleared up all their smaller concerns at a kitchen-table summit, the larger benefit seemed undeniable. “We said, ‘This isn't about you or me. This is about what's good for our families,’” Alison says. "‘And it's good for our kids to grow up across the street from each other.’"

That balance of independence and togetherness has been upheld. The sisters may be best friends, the husbands close, and the children virtually interchangeable (they have only recently come to understand, for example, that some of them are cousins, not brothers and sisters), but Aileen and Alison maintain a sensitivity to the needs of each separate family.

Aileen's highly organized daily schedule juggles those needs visibly as she navigates the children through school pickups and piano lessons, toddler mediation and cookie baking. "Crazy Wednesdays" are her busiest days — in addition to picking up Hunter, Anna, and one of Anna's friends from kindergarten before lunch, she must then drop off Anna at gymnastics class. A babysitter then relieves Aileen of child care for two hours so she can go grocery shopping and run errands. While Aileen is gone, Anna is picked up by another parent for a 45-minute drawing class and returned just in time for dinner, at 5:45. Alison and "the boys" arrive home from work between 6:00 and 6:30.