I am descendant from Conrad Neihardt/Neuhart & Eva Sauerbrey. Much of what I know comes from Dennis Kastens' 4 volume work "Neuhart Chronicle". According to Kastens' work the Neuharts were from Rumbach in the Pfalz in Germany and three brothers emigrated at different times.Conrad, Sr. emigrated in 1754 to Reading in Berks Co., PA. He married Eva Sauerbrey of Reading who had emigrated with her parents in 1750. Conrad's brother Michael emigrated in 1737 and his family is covered in vol. 2. Brother Jacob came over in 1766 and he and Conrad's descendants are in vol. 3. I only have vol. 3 (1984) and don't know of the availability of any of the volumes.
Kastens has an interesting discussion on the origin and various spellings of Neuhart/Niehardt. His conclusion is that we were Neuharts of various spellings - Nauert, Nawert, Newhart, etc. There were German families who spelled their names Neihardt but Kastens states that there is no known connection between the Neihardts and our Neuharts. Somewhere in America (movie title?), somehow the name evolved to Neihardt, Nihart, Nihardt.
I can help with descendants of Jacob and Conrad but sadly, vol. 3 is not indexed and is kind of tricky to navigate.