Spelling of Herwig

Is it possible that Herwig was once spelled Herweg? My great-grandfather was Herman Henry Herweg, born in 1833. He is buried in Spring Grove Cemetery, Cincinnati, OH. He died in 1903. He was an immigrant from Germany, I believe in the early 1850's. this is what I am trying to find out. He lived in Cincinnati his whole life. Any information you can give me will be most helpful. Thank you.