I noted that you listed PHILLIP MUSGROVE as the father of JOHN SMITH MUSGROVE. Perhaps you acquired this information based on a old family history written in the late 1800's or early 1900's, which was flawed compared to official records, although some of the data was very good.
At any rate, I am prone to believe that the father of JOHN SMITH MUSGROVE of Newberry Co., SC, Emanual Co., GA, then Barbour, Dale, Coffee and Monroe Counties, AL, was actually SMITH MUSGROVE, the youngest brother of PHILLIP MUSGROVE.
SMITH MUSGROVE was never mentioned in the old history is why he was not considered as a candidate. The old history also indicated that the three brothers mentioned, JOHN (III), WILLIAM T., and PHILLIP, had no sisters; but records seem to indicate they had at least three sisters, maybe more.
SMITH MUSGROVE and his second oldest brother, WILLIAM MUSGROVE were both witnesses in a Court case in Newberry Co., SC on 6 Nov 1792. Later SMITH MUSGROVE appeared on a 1798 Road Tax List in Augusta, Richmond Co., Georgia.
There is no indication that PHILLIP MUSGROVE was still living in 1790 or ever went to Georgia. Although, most of Georgia's early census records were lost in the War of 1812, there are many other records of that time available during that period that show older brothers, JOHN (III) and WILLIAM; but none for PHILLIP and only one for SMITH MUSGROVE.
(There is a possibility that SMITH and PHILLIP were the same person, however; but that would be odd that PHILLIP was named in various court records but without a middle name, so why would he later change?)
Keeping in mind that JOHN S. MUSGROVE's was born about 1800 in SC, his only known sister, SOPHIA MUSGROVE (who married MICHAEL LIGHTNER aka LEITNER) was born October 1801 in Georgia; died 18 May 1853, Barbour Co., AL, according to her monument. This suggests that if SMITH MUSGROVE was their father, then he returned to SC before 1800, when JOHN S. MUSGROVE was born, then returned to Georgia, by 1801, when SOPHIA MUSGROVE was born.
I suspect he returned as assisted in the escape of his brother, WILLIAM MUSGROVE and WM's brother-in-law, NATHAN TAIT from the Hancock Co., GA, jail, where they had been sentenced to hang for forgery. The escape took place in February 1801.
Since SMITH is not mentioned after that time, perhaps he died during that escape and his young widow was expecting her second child, SOPHIA, who was born in October, eight months later. She probably remarried and moved to Emanual Co., GA, with her two young children.
SOPHIA and husband, MICHAEL LIGHTNER, who were on the 1820 census in Emanual Co., GA, moved with many members of the LEITNER aka LIGHTNER family to Florida. They than moved northward into Alabama, into Barbour Co., AL (then part of Pike Co., AL). They were joined by her brother, JOHN S. MUSGROVE, in 1833 according to a Tax List of that hear. He was residing in Dale Co., AL, in 1841 when he entered federal land in what would become Coffee Co., AL, when that County was created out of Dale.
The 1830 US Census shows JOHN MUSGROVE in Emanual Co., GA. He was also on a list that showed he had fought in the War of 1812, and he was from Emanual Co., GA, which was probably in the year of 1818, when the fighting seems to have been going on in that State. His first cousins, LARKIN C. MUSGROVE and JOHN E. MUSGROVE, were also on that list stating they were from Baker Co., GA.
One gatherer of family history confused JOHN E. with JOHN S. MUSGROVE, indicating that JOHN S. MUSGROVE was in Baker Co., AL, in 1840 but that was his cousin, JOHN E. MUSGROVE. JOHN S. MUGROVE did not appear on an 1840 census, but his land record showed he was residing in Dale Co., AL, in 1841. He was probably in transit since he was not enumerated in 1840.
Also joining SOPHIA and brother JOHN MUSGROVE, was a JOSEPH MUSGROVE, parents unidentified, who married in Barbour Co., AL; but did not appear on a tax list or census.
Later, in Coffee Co., AL, JOHN S. MUSGROVE was joined by two of his first cousins, LARKIN C. MUSGROVE, and WILLIS S. MUSGROVE. They bought adjacent land, but then moved before 1850 to Florida. (Since we don't know the age of the latter two, they could have been sons of a cousin since those two names were often repeated in the family of JOHN MUSGROVE III, uncle of JOHN S. MUSGROVE).
I hope this information in helpful. It doesn't prove the father of JOHN S. MUSGROVE; but it shows another possibility. I am inclined to believe this version, expecially since I didn't note that PHILLIP was not a name chosen in his descendents, which is unusual if PHILLIP MUSGROVE was his father and his children's grandfather.
What is badly needed in the final estate distribution of JOHN MUSGROVE II, in Newberry Co., AL, after the two known estate sales. Somewhere there should be a distribution of the monies from the estate sales, the first in Abbeville, where the District Court for the 96th District was located and the second in Newberry Co., AL, once they had a county court system. We also need to know the final distribution of wife, ARMINTA (GORDON?) MUSGROVE WILLSON's estate.