Re: Henry ROBERTS' DAUGHTER's-birth year ?
I have a couple of thoughts.
You said the information about Isabel came from a Roberts family letter in the First Families of Tennessee.Who wrote the letter?Was it written by a person contemporary to the time or by someone several generations removed?That would make a significant difference as to how much weight the letter should be given.
The Roberts families - John, Henry, David and William were all in Fincastle County, Virginia ( now Sullivan County, TN) by 1774.William, Henry and David are listed on the pay rolls for Capt. Looney in Fincastle County, VA during Dunmore's War in 1774-1775. (Virginia Archives)
This is where a knowledge of the jurisdictions becomes important.
Present day SULLIVAN COUNTY, Tennessee, was in:
1738 - 1769 Augusta Co, Virginia
1769 - 1772 Botetourt Co, Virginia
1772 - 1777 Fincastle Co, Virginia***
1777 - 1779 Washington Co, Virginia ****
1779 - 1796 Sullivan Co, North Carolina
1796 - Present Sullivan Co, Tennessee *****
Prior to 1779 the portion of what is now Sullivan County north of the Holston River was believed to be in Virginia while south of the river was Washington District NC. The first grants were issued by Virginia for lands north of the Holston.
In 1787 Sullivan County was part of North Carolina, as it fell primarily south of the Holston River.In 1787 Sullivan County was divided and Hawkins and Greene counties were formed.In 1790 North Carolina ceded her lands west of the Great Smokey Mountains to the Federal Government.The territory was known as the Territory of the US South of the River Ohio.Knox County was formed from Hawkins and Greene Counties in 1792 and Tennessee became a state in 1796.
In order to follow this family one must check out records in all these counties and states.Both Henry and William did obtain grants from the state of North Carolina but that does not necessarily mean that they had actually changed states.It simply meant that the land they were granted fell into the jurisdiction of North Carolina.
John and all his family except for son James died in an Indian raid 24 Sept 1774 when it was Fincastle County, VA.David died in 1779 in the same area but then known as Washington Co., VA, also killed by Indians.David left a wife Susanna and a daughter Sarah.
At the time David died, there was an attack on Henry's Mill and one of Henry's daughters was taken.What this means is that the children of David, John and Henry were born in the 1770- 1780 time frame.Therefore, Isabel, daughter of Henry, cannot be your Isabel.
This only leaves the next generation - the children of Henry and William as possible parents for Isabel.
William (1) had only one son named in his will and that was William (II) born 1780-1790 ( 1830 Knox Co census).He is the man I have in Texas. His children were born between 1804-1831 ( all proven by 1850 Texas census).Partition deeds for William do not name a daughter Isabel or any children who were her issue. The partition deed does mention a deceased daughter and her issue so this wasn't a case of "forgetting" who the deceased kids were.
It is possible that William (I) had more children than just son William.I have only seen an abstract of the will.Other court documents may reveal other children.
Henry had two sons James Alexander and Andrew.Andrew died in 1860 in Knox County.I believe James died in Knox in 1837.Have you check their wills or deeds?
I would investigate Henry's sons further.