I'm pretty sure I connect to this Sommerfeld line through
the brother of my great grandfather. Wilhelm Koss , brother
to Johann Koss ( my great grandfather) married Anna Sommerfeld.

Anna Sommerfeld was born 5 June 1849 in Meszcze. She married Wilhelm Koss (B. August 5, 1846 in Meszcze).

Their children that I know about were Ludwig, born 1874, Karolina born 1880,Emma born in 1886 and Otto born 1888.
Emma had one child that I know about, Martha born May 13, 1908 in Lodz.
Emma was not married when she had Martha.
My information comes from a census that I received from
archives in Poland
Linda