1. As you have rightly suggested, obtain certified family tree starting from the person who had owned the land in entity.
2. Family tree/ Legal heirship Certificate can be obtained from the jurisdictional Tahsildar.
3. After thorough studying of the mother deed and other connected documents, we can know if there are any other rightful claimants and if rightful claimants exist, then corresponding legal documents have to be prepared and to obtain their signatures.
4. There has to be registered Partition Deed to validate division of property.
5. Regarding title, Encumbrance Certificate, etc, of the document, Sub Registrar's Office of the jurisdiction will be the competent one and for other agricultural documents like. RTC, etc., it can be procured from the jurisdictional Tahsildar's Office.