Matthew Galloway (1759-1824) is my 5G grandfather and I have been researching him for 22 years.
I have also spent the last 4 years doing intensive, almost nothing but Matthew Galloway research.

If you descend from that William J. B. Galloway b/ Darlington Co, SC with Henry Co, AL ties, you do NOT descend from Matthew Galloway b/ 1759.

Researchers have crossed 2 unrelated lines. Your William was NOT ever in Oglethorpe Co, GA nor married to a Polly Ragan from the research I have been able to find. (If she was a Polly Ragan, of which I am highly skeptical, she was NOT the Polly of Oglethorpe who married William Galloway in 1805 Oglethorpe as that is my William, son of Matthew).

If I am not mistaken (I have researched the Henry Co, AL Galloways to a degree, just to be able to sort them from mine & inform others), your William is probably the son of an Absalom Galloway (don't quote me on that), but in any case, there were already Galloways in Henry Co, AL by about 1826, including your William, thus he cannot feasibly be my William of Oglethorpe and Elbert Co, GA.

My William Galloway (son of Matthew) was last found in 1840 Elbert Co, GA and while he is believed to have died between 1840 and 1850 there in Elbert, his widow, his 2nd wife Mary Green Galloway, cannot be found in 1850 either. But by 1860, she is in DeKalb Co, AL living with a stepdaughter, so William is thought certainly dead by 1860, if not by 1850. (Mary Polly Ragan Galloway, his 1st wife, must have died before Nov 1830, Oglethorpe when he m2 Mary Green).

My Galloway line has no known connections to either Darlington Co, SC or Henry Co, AL, so that is one easy way to know the difference between these 2 Galloway lines, even if you come upon crossed trees with bad information. My Galloways came from NC, no known connection to SC, to Wilkes Co, GA by about 1790-1791, then to Oglethorpe, where Matthew died. Son William and his kids lived in Elbert, then other children went to Madison and Lawrence Co, AL in NE Al by about 1817-1820, a few others followed between about 1824-1830 and Matthew's son Thomas went to Walton Co, GA.

Also, though many have crossed the children of my William with the children of your William, one way to tell them apart further is that my GA branch has no known Huttos or Brannons.
Matthew's children were William and Levi, by his first wife, Wiley, Anderson, Brittain, James, Thomas, Sarah A. (Sally), and Nathan Johnson by his 2nd wife.

My William's known children were: Nancy, Michael Beaver, Martha, Matthew A. (my ancestor), Cornelius T., William Ragan, Levi C, Sarah (Sally), Sina. William m1 Mary Polly Ragan, daughter of Mark Ragan and Ann Hamilton and m2 Mary Green. Mark Ragan, like Matthew's son Thomas, also moved to Walton Co, GA. William was b/ 8 Nov 1782, NC.

I hope this helps.

Briana