4/8/2018: John Tennison had a brother named Ignatious Tennison, who can be found on the will of Peter Smith in Caswell, NC; who was connected to many families who lived on Hogan's Creek (Round Hill) in Caswell, NC. Ignatious Tennison did not change his last name and married Lucretia Dennis (Dennis was her maiden name). It is likely that John Tennison (Dennis) did not marry Rachel L. Grant until a year before her death in 1797. Rachel L. Grant's previous husband, likely Sameral Samuel Dennis (b. abt 1750 and d. 1786 in Caswell Co., NC), had died a short time after the birth of her last child (?Elisha Hudson Dennis). We know that on James Grants' will of 1805 (father to Rachel L. Grant) that he mentions that his daughter Rachel was already dead with only one child, thus she would receive nothing. Rachel L. Grant Dennis had children (specifically Samuel Dennis; who had a daughter named Rachel L. Grant and Elisha Dennis who was b. abt 1784 a short time before Sameral Samuel Dennis died in Caswell). Rachel was married to Samuel Dennis prior to marrying John Tennison as was Elizabeth Betsy Cheatwood married to a Dennis prior to marrying John Tennison. UPDATE: Looking closer at the will for John Tennison Dennis, it becomes clearer that his third wife Elizabeth Cheatwood Dennis likely had children from a previous marriage. Here is an excerpt of the will: John Tennison - Will - 18 Dec 1807 - Wife Elizabeth Cheatwood. ***HER 5 children Asariah, Reubin, Polly Hariott, Nancy, Gregory - 5 last children are ***MY 5 last children: my 3 sons Levi, John, James, daughter Coos? - 4 daughters: Elizabeth, wife of Henry Cobb, Anna wife of William Cobb, Catherine wife of Asa Cox, and Ceasy. Exec: son Levi: Wit: David Powell, Turner Patterson (husband to Celia), and Wm. Tapacott. +++Also: We do find a John Dennis and a wife Mary Slater Dennis in Orange Co., NC where records of land grants can be found for 1759 and 1761. This John Dennis (not a Tennison) moves later to Georgia. This John Dennis (not Tennison) appears to be the father of Lucretia Dennis who married Ignatious Tennison; brother to John Tennison. To complicate matters for researchers, both Tennison brothers appeared to have used the last name of Dennis interchangeably with Tennison; but Ignatious Tennison in the end does not change his last name as does his brother John. The John Dennis b. abt 1720 to 1726 in NJ was a son to Samuel Dennis and Ruth Tindall Dennis; immigrating to New Jersey from Ireland before marriage in 1711 in NJ or Pennsylvania. We know, therefore, that it is likely that John Tennisons' 2nd wife Rachel L. Grant and 3rd wife Elizabeth Betsey Cheatwood were married into the Dennis family before marrying John Tennison. We do know now that it was highly likely that both Rachel L. Grant Dennis Tennison and Elizabeth Betsey Chitwood/Cheatwood Dennis Tennison (Lyons) both knew each other and quite possibly met in Virginia before emigrating to North Carolina. Both Rachel Grant and Elizabeth Betsey Cheatwood have ties to the Irby families in Henrico and Chesterfield, VA areas, as well as Orange and then Caswell Co., NC. Specifically, Rachel L. Grant's brother John Grant married Rebecca Ann Irby who was a daughter of Peter Irby and Elizabeth Cooke Irby and Elizabeth Betsey Cheatwood's Uncle Mathias Chitwood/Cheatwood can be found on court records of 1759 for Penelope Irby Parrott, who was contesting the will of her father Dr. Joshua Irby in Chesterfield, VA.

The following information from Diane Clark Smith:

John was born John Tennison to Ignatius and Elizabeth Nevitt in Charles County, Maryland while Maryland was till a colony. Elizabeth Nevitt was married previously to a planter named Daniel McPherson who died in 1740.

Notes by Diane Clark Smith:
The name of his first wife is lost to history. She died about 1791 leaving 7 children:
Catherine m. Asa Cox
Levi m. Susan White
Celia m. Turner Patterson
Mary Anna m. William Cobb
John "Jack", Jr m. Mary Arnett
Elizabeth m. Henry Cobb
James P. m. Betsy Chadwick and #2 Parnina Gunnels

John's third wife was Elizabeth "Betsey" Cheatwood, daughter of William Cheatwood and Jean Flourney of Powhattan County, Virginia. It is possible that Elizabeth Cheatwood was married to another Dennis, resulting in the children below as described by researcher Diane Clark Smith:
Asariah Dennis m. Elizabeth Taylor
Reuben Cartwright Dennis m. Susannah Arnett moved to Illinois Mary "Polly" Dennis m. unknown Gunnels Harriet Gregory Dennis m. Joseph J. Knox in Tennessee Nancy Dennis m. William Grant White in Tennessee