krohn family history,late german

I am beginning a search of the krohn family prior to my grandfather,werner krohn of berlin moving to saginaw mi. with his second wife lucy and his two children joachim and brigette right after wwII. My great grandfather otto and his wife emma krohn had immigrated to saginaw some years prior and was sponsor to werner. would like any prior history,meaning of name, coat of arms etc. E-mail harkrohn@hotmail.com