Both Sikorski and Piasecki created early twin engine helicopters. I believe Sikorski was actually first with the CH-37 Mojave sold to the US Marines in 1954.
there are a few twin rotor helicopters. The Chinook is possibly most famous.
Helicopters - band - was created in 1980.
Russian Helicopters was created in 2007.
Columbia Helicopters was created in 1957.
Hughes Helicopters was created in 1947.
Bristow Helicopters was created in 1953.
Bendix Helicopters was created in 1942.
Universal Helicopters was created in 1963.
Gulf Helicopters was created in 1970.
Canadian Helicopters was created in 1987.
Carson Helicopters was created in 1963.
Bajan Helicopters was created in 1989.