Stephanie,
You are correct that one of Christian I daughters is the grandmother of George Custer. I will send you some information that I have. I am also the ggg grandaughter of Christian III. My gg grandfather was Israel Garlitz who was married to Agnes McKenzie. Israel had the following siblings-Solomon, Samuel, John, Elizabeth, Elinora, Joanna, Henry, Moses and William. Do you have any background on Christian III's wife Sarah? I have hit a roadblock with her side of the family.

Judy