Hi, Winslow phone books would be helpful. Try calling the Winslow libr, and ask for the old phone books for 1968 and see if they can xerox the phone book page.
With that many siblings, you should be able to find.

Also what agency was involved? Write a contact waiver and have it put in the agency file.
See if they put a contact wiaver in there too. Are you Native american? If so, maybe the state will give you more information based on the Laws for Native american people.

Joan