This is interesting; after believing there were not very many Nills left in the US, I've come across quite a few. Have you done very much research on this family?
I think this is all the same family, but I haven't made the connection yet. My great grandfather was Solomon and he had brothers named George and Conrad. Before 1850 they went to OH with their parents, George and Mary. However, I think some of them went to IN for a time and then returned to OH. Solomon's family went to OK and to CA. If I connect them up to your names, I'll let you know.