My gr-gr-grandmother, Catherine Niemeyer, born 1820 Warmeloh, came to US [Pennsylvania] in 1866 with six young children. Catherine had male sibs: Johann Heinrich, born 1807; Friedrich Wilhelm born 1810 [arrived US before 1866]; Johann Dieterich 1813-1836 unmarried; and Heinrich August, born 1823. I do not have research on desc. of Johann Heinrich nor Heinrich August or any definite connection to Neimeyer you mentioned. Sorry.