Thanks so much for you reply, Donna. This really clears up a lot of things. I'll email you privately later (I'm thinking of driving up to San Bruno to the Natl Archives today) but I have a couple of quick thoughts:
We know from the Elizabeth Brewer newspaper bio published decades ago that there were 8 siblings. I've seen a William listed in some genealogies but no proof. But there are several mentions of a David Cooley in Stokes county NC in the 1810s, just after Edward was supposed to have left for Indiana. I think there's a better chance that he was the 8th child. Perhaps he and his were the unknown heirs. All the other children seem to be well accounted for.
I have an interesting theory going for Edward. He helped establish the Methodist Church in Stokes county in the 1790s by giving some land. You may be aware of the Cooley Meeting House near Salem IN that may have sat on his land. Apparently, yearly meetings for the southern Illinois Methodists took place there, signifying its importance. Those meetings seemed to stop after his Edward's death which, in itself, could be significant. And, as you probably know, a major political position of the Church was abolition. Edward owned no slaves, nor did his father, John. I've read some indications that Salem may have been a hotbed of abolitionist activity. It's obvious, I guess, where I'm going on this. I'd love to know what you think about that.