We know that John had a son Abraham since it was Abraham who settled John’s estate and his siblings gave him their release in 1869. Since he was not living with his parents in 1850, he must have been already out on his own. The question is where was he living in the 1850-1870 time period? From Census, using a guess as to his approximate age and assuming some proximity to Union County, there are two candidates: one in Milton and one in Centre County.

I think Abraham of Centre County is the right guy. His wife was Mary Boob. There are death certificates for several children of Abraham Martz and Mary Boob and most say he and Mary born in PA which is not helpful but two say they both were born in Union County.  In Abraham's case, that may or may not be true but I think it for sure places him there earlier in his life.  Also Abraham’s sister, Mary Ann, married Michael Boob. I think Abraham and his sister Mary Ann married Mary Boob and her brother Michael, respectively.

Abraham is designated J1a1.

I have found Abraham in Centre County in 1850-1880.

He and Mary are on find-a-grave. I also found a church death record for him.