I have connections to the POPP and SIEVERT (SIEWERT, SIEFERT, SIEBERT) families in the Marshfield and Auburndale/Wood County, WI and the Spencer and Mannville/Marathon County, WI areas. My great-grandfather, August POPP of Mannville, married Bertha SIEBERT from Auburndale in Spencer on 18 June 1892. August's sister, Alvina, was married to John GAUGER from Marshfield. They had another sister, Anna, who was also married to a GAUGER from Marshfield. If this sounds like it would be helpful to you, contact me and I can give you the information I have.