I had a distant cousin Melinda BOREN b. 2 Sep 1809 Sumner Co., TN, d. 25 May 1877 Kinderhook, Pike Co., IL, marr. 8 Feb 1827 in Wabash Co., IL to Moses DECKER 3rd b. 16 Dec 1806 Knox Co., IN, d. 25 Feb 1884 Kinderhook, Pike Co., IL.
Moses 3rd's parents were Moses DECKER Jr. b. 6 Mar 1780 Washington Co., PA, d. 1864 Barry, Pike Co., IL & Christine HARNESS.
Moses Jr.'s parents were Moses DECKER Sr. & Christina _____. Given the areas where Moses 3rd was born & lived, it would seem most likely that he & your John DECKER are related.