Claim on Ancestral Property

Dear Sir, We are a Christian Family. We have an ancestral property for which we are paying House Tax for the last 16 years on our grandfather's name, but he had died in July 1977. And the House Tax is the only document we are having and no other document with us. The original documents have been lost after his death. In November 2006, our father has also died. My grand father left behind a son and a daughter of which daughter is still alive with her children { 1 son & 2 daughters } and grand children. My father and his sister were married before 1969. My father left behind a widow & four children { 2 son's & 2 daughter's }. Younger daughter was married in Oct 2014 and younger son was married in Feb 2006 and he has two daughters. Now, we want to partition that ancestral property. Please suggest as to how we should partition that property legally and who gets how much share and have a legal document which is registered on our name. Also, please suggest if it can be registered under one name and have a legal registered document & also the procedure so that we can sale the property & distribute the amount later.