Thank you for the personal email to alert me to your post. Wow, this surprised me. I haven't had a chance to look for more information about the children, but am particularly interested in John C.I found a John D. in St. Clair County, born 1820 SC. He would be closer to the ages of Jesse and Samuel.
As for Zedock/Zachariah. My guess is they are the same person, but have no way of knowing. Zadock's son, Zadock Jr., had the middle initial H.
As for Emberson Brewer (b. abt.1802), if he was a son to this John Brewer of Franklin Co., TN, he would not have been mentioned in the will since he died about 20 years earlier in Missouri.
I've never fully understood the 1820 census but Ancestry.com customer help said there are two males within the ages of 16 to 25 in John Brewer's household, Franklin Co., TN.If John C., mentioned in the wil, is not within this age group, there still seems to be one male who could have been Emberson.Unless Zadock and Zachariah are two; then the other son could be Zach.(Joseph was about 12).
I wonder why Jesse and Samuel weren't mentioned; maybe they had second names they used.
Thank you so much for posting this information. I'll try to find more about Zachariah and send what I find. Jackie