There are 2 branches of the Yellis (Julius) Kassel descendents, one tracing from Johannes came to Philadelphia with William Penn around March 20 1686, died 1692. Johannes brother appears to have been killed without issue by indians near Pittsburgh.Johannes son Arnold seems to be the connection to this family. This branch remained in PA, and is well documented. Typically they opted for the spelling Cassel.
The other branch descended from Heinrich Kassel VON GEROLSHEIM, who arrived in early 1700s and died in PA in 1726. His son, Heinrich "Henry" Cassel moved to Wakefield Valley MD, where he and many descendents are buried in a family cemetery. Two of his sons moved to Kentucky, while my ancester stayed in Wakefield and began using Cassell.
Any Castles, must be in Johannes side, or from totally different origins. The name Kassel may come somehow from Hesse-Kassel Germany, but I have yet to find Yellis in that area. He was a respected and published Mennonite minister, who lived in the Worms area of the Rhine River area. Because of the constant war and perhaps preaching assignments, he moved around that region. It is possible that his family came from Switzerland, don;t know exactly. Hope this helps, Clay Foreman