What do you mean by ''none of the property has clear documents"? Are the documents of title also lacking? As per the facts furnished by you, the properties date back to 1948. Is your grand father the original purchaser of the properties or the site underneath it? The original purchaser must have registered the deeds. You may carry out a title search with the registrar.
It remains to be seen whether on the basis of the documents, if any, in the possession of your grand father a case of continued possession can be set up by your father if your uncle files a case to restrain him from developing the property as he is opposed to it. Your father may also file a case for partition of the property if there is a semblance of title. To this end, you should have an in chamber consultation with a lawyer.