On March 22, 2021, about 1230 central daylight time, a Piper PA-30 airplane, N7588Y, was substantially damaged when it was involved in an accident near Wanatah, Indiana. The two commercial pilots were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot was practicing instrument approaches with a safety pilot. While in cruise flight after about 2.6 flight hours, the left engine lost power and the pilot diverted toward Porter County Airport (VPZ), Valparaiso, Indiana. The pilot subsequently feathered the left engine propeller to reduce drag. While the airplane was on final approach, the right engine lost power and the pilot made a forced landing into a field, which damaged the fuselage skin and longerons. The pilots recalled that both respective fuel selectors were in the auxiliary tank position. Although both pilots thought the respective auxiliary tank fuel gages indicated more than ½ full when the engines lost power, examination revealed that both auxiliary fuel tanks were empty, while both inboard fuel tanks were nearly full. No evidence of fuel contamination or fuel leaks were observed and both auxiliary fuel tank gauges indicated empty. No anomalies were noted with the engine-driven fuel pumps or fuel boost pumps. Both auxiliary fuel tanks were serviced with 5 gallons of fuel, and the tank gauges increased to a level that corresponded to the fuel added.