My grandfather's name was William Marcus Greve and he left Schlesswig in 1868. He had a brother named Conrad Christian Greve. They had three half brothers, Fritz, Heinrich, and Johannes who were older. In 1867 when their father, Johann Friedrich Greve died, Willhelm was 19 years old, Conrad was 16, Heinrich was 28,Johannes was 26. At that time Fritz was married with one child and living in New York City and was about 31 years old.
I have more information if you are interested. you can E-Mail me at Billgic@optonline.net