Since you were close to his brother's family, I would sujeggest you start with thier dad to see if you can find out his line back. Also if you have a deadth date of your grandfather, or an obituary, check with the Mortuary that was in charge. Sometimes they will release family information that could be of help. Also the cemetery records could also be of help to find out who his next of kin, where he came from, etc.
Try some of the Genealogy Societies in your area, the libraries also have microfilm that could be of help.