Maybe they are going above the federal mandate djplong. But the fact remains, "The Affordable Care Act allows young adults to stay on their parents’ health care plan until age 26," according to the US Dept. of Health and Human Services website.
Read it yourself. There are stipulations. For instance, the "child" can't be employed with a company that offers health insurance and the "child" must be claimed as a dependent be the parent/s for tax purposes.

http://www.hhs.gov/ociio/regulations...act_sheet.html