Clues gathered so far:

1. Nicholas Naylor was listed in the Migrations Project with a destination of Madison Co, Kentucky along with George Naylor (son of Batson Naylor). George Naylor died in Madison Co, KY in 1836.
2. Nicholas, Benjamin (son of Batson) and James Naylor were listed on the 1800 Green Co, KY Tax List.
3. Nicholas married Mary Selby in Prince Georges, MD; Benjamin Naylor married Deborah Selby in Prince Georges, MD; Benjamin Fowler married Mary Naylor in MD.
4. Nicholas Naylor was in Madison, Pike, Indiana in 1820 as was Thomas Fowler, probable nephew of Benjamin Fowler.
5. Benjamin Fowler was listed on the 1800 Madison Co, KY Tax List along with Jeremiah and Joseph Fowler.
6. Nicholas Naylor is listed on the 1783 Tax List of Upper Marlborough, Prince Georges, MD.  Batson Naylor (Junior) is listed on the 1781 Tax List of Upper Marlborough, Prince Georges, MD.  Benjamin Naylor is listed on the 1785 Tax List of Upper Marlborough, Prince Georges, MD.  Richard and William Fowler (possible first cousins of Benjamin Fowler) were listed on the 1779 and 1786 Tax List of Upper Marlborough, Prince Georges, MD.
7.  Richard Fowler, son of Jeremiah Fowler and Drucilla Isaac, died in Madison Co, KY in 1817. 
8.  Joshua Selby, grandson of William MacGruder Selby, was in Madison, Pike Co, Indiana in 1820.  His uncle, Joshua Wilson Selby married Sarah Fowler, daughter of Jeremiah Fowler and Drucilla Isaac.  Mary Selby who married Benjamin Fowler was the aunt of Joshua Selby.
9. ANCESTRY.COM MESSAGE BOARD - ADAIR, KY
Searching for Zion Baptist Church records in Adair County, Ky., Glens Fork, 1802-1896. In response to Bruce Patterson:Bruce, we are related thru old James Wilson Selby's son, Greenberry Selby (my ancestor) and yours, Sarah. The other brothers and sisters are Elizabeth, Polly, Joshua, James Jr., Simeon and Lloyd. These folks came from Prince George County, Md in 1798 (see Green County, Ky land entries). James Wilson Selby's brothers and sisters are Josiah, Lingan, Jeremiah, Thomas, and Zachariah. James and all his brothers and father, William Magruder Selby all served in the Revolutionary War (see Oath of Allegiance, 1776, Muster Roles, Archives of Maryland, Vol 18). William Magruder Selby died and his widow Martha Wilson Selby all came to Kentucky (see Adair Co Ky deed regarding Martha appointing NICHOLAS NAYLOR to sell slaves back in Prince George County, Md.)
10.  Nicholas Naylor (spelled Nalor) was on the 1789 Fayette Co, KY tax list along with John Fowler.  This John Fowler has not been identified but it is believed he was related to Benjamin Fowler - possibly a brother.
11.  Benjamin Naylor, the son of Batson Naylor and Margaret Fields, named his son James Nicholas Naylor.  He could have given the middle name Nicholas because he had a cousin named Nicholas.
12. Zachariah Selby, the first cousin of Mary Selby who married Nicholas Naylor, was listed on the 1807 and 1808 Butler Co, Ohio Tax List.  Butler Co, OH is where Benjamin Fowler and Mary Naylor Fowler lived in 1820.   Zachariah was also in Butler Co, OH in 1820 and 1830.

Putting the clues together it appears that Nicholas and Mary Naylor were closely related to Batson Naylor and Margaret Fields. Nicholas was not mentioned in the will of Batson Naylor so he may have been a cousin or nephew. 

Nicholas enlisted in the Continental Service of Maryland in the Revolutionary War along with an Alexander Naylor on Dec. 10, 1776.  Alexander was born about 1756 probably in Maryland.  He married Magdalena Unknown and Mary Mills and had one known son, Samuel, and two other sons whose first names are not known.  It is possible that Alexander was the brother of Nicholas and Mary.  The parents of Alexander are not known, however, Alexander married Mary Mills in Frederick, MD, and this is where Isaac Naylor and Barbara Goodman were married a few years earlier.  Isaac's parents were George Naylor and Vilanda Isaac.  It is believed that Vilanda Isaac was the sister of Drucilla Isaac who married Jeremiah Fowler (relative of Benjamin Fowler).  It is quite likely that Alexander, Nicholas and Mary were children of George Naylor and Vilanda Isaac.

1820 census - Madison, Pike, IN 1820
Nicholas Nailer (000001-00001) age 45+ Image 2
2 LINES AWAY: Jeremiah Selby (100101-01200) oldest male age 45+ Image 2
Z F Selby (000020-04101) Image 2  (Zachariah)
Thomas Fowler (100010-10100) oldest male age 26-45 Image 2
John Selby (000201-00001) oldest male age 45+ Image 2
Thomas Selby (100001-00001) oldest male age 45+ Image 2
NEXT LINE: Joshua Selby (200010-20010) oldest male age 26-45 Image 2
William Fowler (Washington Twp, Pike, IN) (100010-20010) oldest male age 26-45 Image 2

EARLY MARYLAND RECORDS:
NICHOLAS NAYLOR MD Prince George's County Upper Marlborough 1783 (probable brother of Mary Naylor)
BATSON NAYLOR MD Prince George's County Upper Marlborough 1778 (possible brother of Nicholas and Mary Naylor)
BENJAMIN NAYLOR MD Prince George's County Upper Marlborough 1785 (brother of Batson Naylor Jr.)
BENJAMIN NAYLOR MD Prince George's County Upper Marlborough 1793 (brother of Batson Naylor Jr.)
BENJAMIN NAYLOR MD Prince George's County Upper Marlborough 1797 (brother of Batson Naylor Jr.)
RICHARD FOWLER MD Prince George's County Upper Marlborough 1779 (probable 1st cousin of Benjamin Fowler)
WILLIAM FOWLER MD Prince George's County Upper Marlborough 1786 (probable 1st cousin of Benjamin Fowler)
WILLIAM FOWLER MD Prince George's County Upper Marlborough 1788 (probable 1st cousin of Benjamin Fowler)
WILLIAM FOWLER MD Prince George's County Upper Marlborough 1799 (probable 1st cousin of Benjamin Fowler)