What I have found about Clement Mattingly is that he arrived by boat a few years or so after Walter was born. I found the ships log for him, as I ran that lead too, and show it below
This would be the first Clement Mattingly that I know of, and it placed him arriving three years later than Walter's birth (abt. 1738). I would say he is blood relation to Cesar, but what cousin he would be, I don't know.
Name: Clement Mattingly
Arrival: 1738 - Maryland
Source Publication Code: 1243
Primary Immigrant: Mattingly, Clement
Annotation: Date and place of mention in land survey. County and name of land purchased are provided. Originalrecords are contained in Land Office Registers, indexed starting on page vii of the introduction.
Source Bibliography: COLDHAM, PETER WILSON. Settlers Of Maryland 1679 - 1783. Consolidated Edition. Baltimore: Genealogical Publishing Co., Inc., 2002.
Now, some say Cesar had a son named Thomas, but others think they were speaking of his brother, and was the reason why no will or other documents show up for him. As far as I know, or have seen, nobody has been able to document this Thomas, or where he was buried.
If there was indeed a Thomas Mattingly, who would have been Cesar's son, he could have been Walters father, but I'm doubting that myself. When Walter was born, there wasn't but a few who could have been his father, actually, only two documented that I know of. Those two would have been John Mattingly, Cesar's son, or Ignatius Mattingly, Thomas II's son. That is, unless, there were some other Mattingly's who were around that part of Maryland that we don't know about during 1735.
Also, by now knowing that Walter lived around Richard and Mark, Johns son's, and Richard moved with Walter, I would say they were close family. At the time of the Revolution, Virginia's west country was just being settled, and that explains why Walter and Richard moved to where they did.
Anyhow, below is the deed information I have found for any who might need it.
From Paul Mattingly, Atlanta, GA.
>From book Fairfax Co, VA Wills:
pg 24] Branner (Brammer?), Mary 8 Jun 1754/16 Sep 1765.
Sons: John & Henry, grson Thomas Heartsen. Exec: son John.
Witnesses: Walter & Liddy Mattingly, Mary Simmons
pg 27] Robertson, James, Sr. 4 Sep 1768/Feb 1769
Daus: Jennett Bowmaker Robertson & Elizabeth. Sons: John & James, grsdau Elizabeth Robertson, d/o James Jr.
Witnesses: Charles Craig, Nelson Reed, James Mattingly
<< g 24] Branner (Brammer?), Mary 8 Jun 1754/16 Sep 1765. >>
xxxxx Correction (my lousy typo) date above Jun 1765/Sep 1765.
Halifax Co, VA
Entry Record Book 1770-1796 Land Records:
18 Oct 1787 William Matherley, 126A on Bars of Fall Creek, beg Smith's corner, desc. follows.
Mattenley (Matenly): Mark, Richard, Walter
#41 Mar 1778 Mark Mattenly, 400A beg at poplar in his plantation, desc follows.
#55, 15 Aug 1785 Richard Matenly, 300A on head of Strawbberry Creek. #35 1773 Walter Mattenley, 400A joining Constant Perkins & Peter Perkins Line.
1778-80 Tax Lists:
Farris: Wm. Lomax, Randolph, Harmer & Co. Mayo: Valentine.
Lindsay: John. Cooper: John, Thomas, Joseph. Parker: Samuel, John. Mattingley, Walter, Richard.
Heads of Families in VA 1783:
Mattley Joseph p 41 Pittsylvania Co 9 w, 12 blk
" Daniel p 41 " 1 w 0 blk
>From "Fairfax Co, VA Will Book A 1742-52 and Will Book B 1752-67":
8 Jun 1765 will of Mary Brawner of Fairfax. Will witnessed by Liddy Mattingly and Walter Mattingly
>From "Pittsylvania Co, VA Deeds 1774-1778":
Page 202. Apr 12, 1776 from Walter Mattinly of Pittsylvania to Sylvester Adams, for 60 lbs sterling, 394 acres in Pittsylvania on both sides of Sandy River, and bounded by Kennon's old line, the river just below the falls, his own line. The land was "sruveyed by George Lumkins by patent"
dated Aug 15, 1764, & by several conveyances came into the possession of Wallter Mattinly, as by Halifax County Court will more full appear. Singed Walter (A his mark) Mattenly. Wit - George Ross, George Adams, Mary Williams, THomas Fletcher, Recorded Apr 25, 1776.
>From "The Militia of Montgomery Co, VA 1777 - 1790":
Listed in Captain William Bobbet's Company - Walter Matenlee
From: "Tax List of Montgomery Co, VA 1782":
Walter Mattinglee - 1 tithable, 0 slaves, 2 horses, 6 cattle, land - yes.
Also listed was a Richard Mattinglee with 1 tithable, 0 slaves, 1 horse, 0 cattle and land - yes.
>From "Washington Co, VA Surveys & Commissioners Certificates 1781-1797":
Surveyed fro Walter Mattingly assignee of Aaron Lewis 134 acres of land in Washington Co in the Rich Valley on the north side of the Laurel fork a branch of the North Fork..... dated 13 Apr 1785.
I will send this to you by e-mail also.