Linda Schweitzer isn't a wallower. The petite blond, 56, is pragmatic and capable. Problems get solved, and little is left unresolved in her life. So when she was darkened by a profound sadness one ordinary Sunday afternoon at her sister-in-law's house in Shelton, Conn., she knew something had to be done.
The cause of her dismay? Call it family-happiness envy. Linda watched her sister-in-law Jan chat with her two grown children as five grandchildren roughhoused on the lawn; everyone lived nearby, and gatherings like this one were spontaneous and commonplace. For Linda and her husband Bill, on the other hand,...