I found a John and a David G. Nicholds living in Benton, Wayne, Missouri in 1870. I believe one of these brothers isyour John.
1870 Benton Wayne, Missouri David G. Nicholds, b. TN, 47 mary C., wife, b. MO, 35 William, b. MO, 17 John, b. MO, 13 Millie, b. MO, 12 David G., b. MO, 8 thomas, b. MO, 3 Layfayette Kirby, stepson, b. MO, 13 Mary J. Kirby, stepdau, b. MO, 11
What led me to this family was the Whitfield Family Tree, ancestry.com and the info provided in it. Most larger public libraries provide free access to Ancestry if you have a library card.
The Leonard family tree, ancestry.com shows David's wife as Mary Catherine King. Her first husband was jesse Rexus Younger Kirby who died in 1860 in Butler Co., MO. Of course you still need to prove all of this but the Leonard family tree does provide sources.
Mary Catherine King Kirby Nicholds was buried in Chapel Hill Cemetery, Wayne County, Missouri. Source: Leonard family tree
I didn't find her in findagrave.com but you can contact the cemetery.
Also do you have a copy of John's obituary? That might mention his parents and siblings. Successful Searching!