I will contact the two researchers I have e-mailed on this family.If they have no problem with sharing, I will forward my e-mails and their responses to you. This will give you some leads to check.
Sophia Groscost and John Decker are my third great grandparents as well so your wife and I are distant cousins!Their son, John G. Decker (1833-1897) married in 1864 Emma Erisman (1845-1887) of Lancaster County. John Decker was with the 77th Pennsylvania Infantry from 1861-1865.I have found most of their children and families in census records up to 1930, also some of his siblings.I also have some newspaper references on a couple of his siblings.My line is through John's daughter, Catherine (1872-1951) who married Martin Mellinger Musser s/o Christian and Elizabeth Mellinger Musser of West Hempfield Twp. near Columbia.
I'd be glad to share what I have so far once I get it better organized(that takes awhile).Please contact me directly at enjardinatfrontiernet.net, substituting the usual symbol for the word if you are interested in corresponding further.Hope to hear from you.