It depends on what you mean exactly by "who invented", but Wilhelm Brenneke invented the 7x64 Brenneke - a very popular, all round cartridge in Europe. The .270 Winchester was later based on it, but given a slightly different bore size so they wouldn't be interchangeable. The .280 Remington, that came much later, is even closer ballistic twin to the 7x64.

Having said all that, (which I think is acknowledged by historians), the 7x64 is designed for a much wider range of bullets, (the same range as the 7x57mm Mauser),and so the throat is quite different to that of the .270 Win., making it quite a different cartridge in practise.