Descendants of Christian Sivertsen

My g. grandfather's brother, Christian Sivertsen from Sandefjord (Sandeherred), Norway, born on September 13th, 1857, emigrated to the US - I do not know when he did or where he settled. In the 1930-s his daugther Kate visited Sandefjord. She was married to P. E. Rust and had two daughters. Any information about the family greatly appreciated. Erling Gogstad, Sandefjord, Norway