Thanks for your wonderful suggestions! Extremely detailed & helpful!
I especially liked seeing the brother MASTENs signatures on the page here, and the land maps:http://www.beaglz.com/francais/JG6.pdf
It turns out that the 1819 Petition does mention a relationship, Jeremiah MASTEN is the son of the Abraham MASTEN in this petition.
My mother has access to the microfilms & I am anxiously awaiting her photocopies of same to see what all the 1819 Petition says. I seem to remember her also saying the 1819 petition mentions Abraham's land grant from his service in the KAR, however my memory isn't as trustworthy as the photocopies will be...
Will update when they arrive.