I have copies of pages from Ancestors of William and John Johnson, Johnston of Caskieben, Crimond and Cayesmill, by Lorand V. Johnson M.D.
William Johnston, Gent. m. 10/12/1723 Ann Chew, dau. Larkin & Hannah Roy Chew. Sheriff Comm. dated 1731 Will 1778 Spotts Family account: "Lord William Johnston, member of House of Lords (Scotland or England), killed his adversary and fled to Virginia."
Joseph Johnston Larin Johnston, b. 1727 Judith Johnston, b 1729 Robert Johnston, b 1726 John Johnston, b 1732 Benjamin Johnston b 1734 James Johnston b 1736 William Johnston b 1738 Hannah Johnston b 1739 Elizabeth Johnston, b. 1742 Richard Johnston b. 1740, d 1788 m. Dorothy (Beverley) Waller. m2: Ann Smith, Caroline Co.
Richard's Children: Which wife is not mentioned
Richard W. Johnston William Johnston Dau. m. --Roy
Augt. 14, 1765 Richard Johnston of Spts. Co. and Dorothy, his wife, there was land transactions with Mary Dawson. Page 311
Witness to several other land transaction in 1766, & 1767
2000 sterling to Joseph Brock, guard. to Richard Johnston, orph. of Richard Johnston, with Edward Herndon, sec. Feby. 5, 1788 Page 313
March 1, 1788 Beverley Winslow of Berkely Par., Spots. Co., to his son, Thomas Winslow, of same par. and co. Deed of Gift. Tract of land purchased of Richd. Johnston in Berkeley par., Spots. Co., etc., No witnesses. April 1, 1788
There is more information. Wife's names, b & d dates, and their issue.