I believe you are correct in following the Hussey line to find the ancestry of Jedediah Garrison.
TIES BETWEEN GARRETSONS & HUSSEYS
The line of Garret Garretson contains many Hussey intermarriages although I have not seen proof of a James Garretson to Hussey marriage.
Garret Garretson born August 4, 1681 in New Castle DE married Charity Hussey born August 4, 1681.
Their daughter Anna Garretson married her first cousin Christopher Hussey September 5, 1736, New Castle, DE.
Garrot & Charity’s son John married as his second wife his first cousin Content Hussey September 5, 1736, New Castle, DE.
This is not an error.Quaker records show that brother & sister married brother & sister in the same “meeting.”Content & Christopher Hussey were the children of John Hussey born 1674 & Ann Inskeep.I have the record which includes the list of witnesses.
Garret & Charity named a son Jedediah.Jedediah Garretson’s will was probated October 22, 1766, New Castle, Delaware.His heirs were: “ Son, Eliakim; James Garretson, son of Cornelius; sisters, Huldah Gooding and Mary Scott; sisters, Sarah and Elizabeth Garretson; sister's dau., Hannah Heney.”Exc. William Sant Clair; sister, Huldah Gooding.
The James Garretson named in Jedediah Garretson’s will as the son of Cornelius is Jedediah’s nephew, son of his brother Cornelius who pre-deceased Jedediah as evidenced in the will of their father, Garret Garretson probated January 6, 1758.
No further proofs are found for this James Garretson.Cornelius date of birth would be after his parents’ marriage in 1700.Cornelius died before his father’s will was written January 20, 1754.He already had two sons, James & John.(John is not mentioned in the will of Jedediah so he must have died 1754-1766)If Cornelius was born soon after his parents’ marriage, his own sons could have been born as early as 1720.
There is a Jedediah Hussey born March 6, 1676 married Esther Cooper August 24, 1705 Philadelphia Monthly Meeting, Pennsylvania, and their son Jedediah Hussey born about 1712.Jedediah Hussey born 1676 was a brother of Charity Hussey who married Garret Garretson.They had a brother Christopher Hussey who married Susan Eliakin and a nephew Christopher Hussey who married Anna Garretson, marriage info given above.
So there are Christophers & Jedediahs aplenty in this Hussey family who had many intermarriages with the family of Garret Garretson of New Castle, DE.
TIES TO NORTH CAROLINA
This Hussey family had several members who appear in the records of Orange and other counties in North Carolina.
Stephen Hussey son of Christopher Hussey & Anna Garretson born September 10, 1739 in Mill Creek Hundred, New Castle, DE married Martha Chamness September 3, 1762 in Orange Co., NC.
The will of Christopher Hussey who married Anna Garretson was probated May 1774 in Guilford Co., NC.
James, the son of Cornelius Garretson, was an orphan, and was a first cousin of Stephen Hussey who married in Orange Co., NC.James Garretson was a first cousin once removed of Christopher Hussey who died in Guilford Co., NC.James was the nephew of Christopher's wife, Anna Garretson.For someone whose father and only sibling had already died, these would have been close relatives.
There may be other ties but time has only permitted this amount of research so far.
Because the Husseys appear to have been in Orange Co NC by 1762, it seems plausible that Cousin James Garretson would have also been there by then.
Karen Descendant of Zebulon Garrison who died in Montgomery Co., IL