I would follow up on research in Jack Co, TX. Check the GenWeb site for that county.
Go to the Oklahoma GenWeb site, click on Inidan Territory.Down in the South Central part of the map, see Chickasaw Nation?Click on that.Scroll down to list of counties included in the Chickasaw Nation.
Most genealogical collections will have a copy of "Map Guide to the U.S. Federal Censuses 1790-1920", it is very easy to see outline of the Chickasaw Nation with overlay of current counties.You can see how much of the "border" counties were included.
My husband has many family members buried in Ponotoc Co, most of which was in the Chickasaw Nation.That was how I learned about "two" territories.I had looked for them in the Oklahoma Territory 1900 census, couldn't find them.Then I stumbled on the fact that there is a separate census for Inidan Territory for 1900.Then I found them.
I would check the 1900 census for Jenny Brown Cannon and her husband.See if you can track down any descendants in that line.See if you can find out who her father was.I know, Brown is not your direct line, but there may be a researcher out there working on the Brown line, that knows something about Nancy. I'm currently trading info with Hutson researchers, who may have info on a Yates brother we know nothing about.Hutsons married into the Yates line.
Post a query on Laura Brown Straley, on the TX GenWeb "unknown" county site.Every GenWeb state not only has a site for each county, but alsoan "unknown" county, too.This is for queries when you know the state, but do not know the county.It worked for me on KY unknown county GenWeb site.I received another generation from a fellow researcher.If you do not have any dates for Laura, you can say in your query that you know her sister Jenny was born about 1875, and married in 1896 in OK.When researchers see queries that include some data, they figure you are a serious researcher. (^_^)Happy Hunting.