Your brother is getting better mileage than you because the Energi’s battery can actually drive on battery power alone for up to 20 miles. That all-electric drive gets 95 MPGe. Once this range is up, the Energi goes back to a similar hybrid system, which gets an EPA-estimated fuel economy of 39 MPG city/highway combined.
Though your 2016 Ford C-Max Hybrid gets practically the same fuel economy on its gas/electric hybrid system—an EPA-estimated 40 MPG combined—the Energi’s 20 miles of electric range give it a small fuel-efficient edge over your car.