Hello WJ
I do not have info on Capt. Thomas siblings children,
like you I have just concentrated mainly on my direct
lines.
BUT, I will do some poking around and see what I can
find, I have pretty good luck doing research.
I cannot remember where I found this info, but, let
me know if it's correct, that way I will have info
to start from.

John Jarnigan II Born 4/8/1775 Danville, Henry Co. Ala.
Died 4/24/1857 Blaine,Grainger Co. TN.
Married: Abt. 1798 Cocke Co. TN
Susanna Clark Born 4/29/1772 VA.

Children:
Thomas abt.1800 Cocke Co. TN
Nancy Ann 8/23/1802 Cocke Co. TN
D. Nelson 2/6/1804 Cocke Co. TN
Francis (male) 9/20/1805 Cocke Co. TN
Mary Abt. 1805 Cocke Co. TN
James abt. 1807 Cocke Co. TN
William Abt. 1810 Cocke Co. TN - 1857 AR

Melinda
(My Mom is the Jarnigan)