Young adults could stay on their parents' health insurance until they turn 26 under a new law pushed by Gov. Rod Blagojevich and approved by the Illinois Senate. The estimated 300,000 twentysomethings who are eligible wouldn't have to live at home, and if they're in the military they could remain covered by their parents they turn 30. They must stay single, however. But business groups could sue to stop the healthcare expansion, which they say will attract unhealthy youngsters and push insurance rates up for everyone.