I don't know of any siblings for Johann Peter Kucher. As he was born about 1712, the Jacob Kucher (b. 1780) you refer to could not have been his brother. Perhaps his grandson? I have the Kucher family Bible (in German), dated 1732, the same year Johann emigrated to America. However, family documentation does not appear in the Bible until the 1790s. No references to Jacob. Interesting about the spelling of your name. I have wondered what variations may have evolved over the years, as the original spelling is hard to find. I'll keep an eye out for Kookers.