Grandma's house is getting a little crowded these days. According to a recent Census Bureau report, 3.9 million children under 18 - 5.5 percent of all kids - lived in houses maintained by their grandparents in 1997. The rate has steadily increased since 1970, when 2.2 million children resided in their grandparents' homes. Children in grandparent-maintained households are more than twice as likely to be black, younger, and living in the South than kids in parent-maintained homes. The grandparents caring for them are more likely to be younger, better educated, and employed than those grandparents who have moved in with their children. In fact, 72 percent of grandfathers and 56 percent of grandmothers in grandparent-maintained households worked in 1996, compared with 33 percent of grandfathers and 24 percent of grandmothers in parent-run households.