My earliest ancestor that we have record of was William Buford Johnston (possibly born (not proven) c. 1680 York Co., VA - died 4 June 1728 Spotsylvania Co., VA) married 21 July 1720 in Middlesex Co., VA to Mary Goodloe, dau. of Henry and Elizabeth Goodloe. They had 2 sons Stephen and Henry. Henry married Agnes Carr Waller, dau. of John Waller and Agnes Carr. Two females later in this Johnston line would then marry their Waller cousins in Kentucky.

William Johnston that married Ann Chew, daughter of Larkin Chew, had a son named Richard Johnston b. c. 1740 - d. c. 1787 that married c. 1762 Dorothy Waller (1743-1770)dau. of William Waller and Ann Stanard.

Dorothy Waller m.(Richard Johnston) was a 1st cousin to Agnes Carr Waller m.(Henry Johnston)

You say you have no record of a Larkin Chew Johnston. I show William Johnston and Ann Chew had a son named Larkin Chew Johnston b. 1 may 1727 - d. 16 Mar. 1816 m. 23 May 1745 to Mary Rogers and they also had a son named Larkin Chew Johnston that died young (b. 1752 - d. 1757)

As to ancestors "lying" I don't find that at all unlikely. Many a story or legend has been passed down through lots of families. Just as an example look at how many people in this same section of this message board claim to be "descended" from Gen. Joseph Eggleston Johnston WHO HAD NO CHILDREN. Also look at how many people claim that J.E. Johnston and A. S. Johnston were cousins when they were NOT, unless somehow related far back many generations in Scotland (which is not proven)
Personally I prefer the truth over family legends. I would rather know I am related to the town grave digger than any peer of the realm if evidence exits for it. Not trying to be mean, just offering what information I have found over many years of genealogical research.