Congratulations on keeping a sibling group together. If you go to this website,
www.nacac.org (North American Council on Adoptable Children), and click on adoption subsidy, you will see a link called "college tuition waiver and scholarship programs." Many states do have special programs for children who are adopted out of the foster care system. I am guessing that is your situation. As you will see, every state has different guidelines, and many states offer nothing at all. For instance, to my knowledge, Georgia does not, but we do have the Hope Scholarship, funded by lottery money. If any child maintains a "b" average in certain core subjects, their college tuition is paid for at a state colege or university. No tax dollars are used.
I suppose we could debate whether parents should accept adoption subsidies or Medicaid, too. I personally think if parents are willing to adopt waiting children, that they should be afforded every break. JMHO.