Your ancestral land was legally distributed in 2007 with a registered deed confirming a 50-50 share. However, an unannounced resurvey in 2017 led to your elder brother acquiring your portion. You can use the registered partition deed and the original 7/12 entry as proof to take legal action. Consider applying to the RDO/SDO to update the Fair Adangal (7/12) with your names, or challenge the new survey and extract entry before a civil court or the collector by making a representation to the Tahsildar and Deputy Collector.