Who was in David rice Atchison family?

Well if what my family has told me about my great-great-great grandfather is true then, the Atchison family was split between North and South. The South siding family spelt their name Atchison while the North side spelt it Atchisson. His ancestors were indentured servants from Northern Ireland who came to America in the 1760's and even were part of the American Revolution.