My wife is a Sonne and grew up in Titusville, PA. Her great grandfather was Herman Mathias Sonne 1836-1886 who died in Bornholm. His son Hans Christian Sonne 1864-1943 emmigrated to Warren, PA and then to Titusville.
Possible that the two lines connect. My email is firstname.lastname@example.org
. We're visiting Bornholm in June.