Their older parents need care. Their kids are still under 18. And they probably have a job, too. They're the 'sandwich generation' -- a longtime nickname for the mostly female, mostly middle-aged group of Americans who serve as caregivers for both older and younger family members at once. A new study estimates there are at least 2.5 million of them, while giving a detailed view into who they are, and which older adults rely on them.
