Individual Details

Isham was likely the witness in this deed of Sarah Johnson in 1765, but his relationship to her is unknown.
12 Jan 1765 Richard Johnson of Hanover Co & Doretha his wife to Sarah Johnson of Louisa, 128£ for land & plantation of Richard Johnson in St. Martins Parish, Louisa Co adj Sarah Johnson & Robert Tenhams corner in Richard Johnson's now Thomas Johnson line, along David Johnson's line, containing 200 acres by patent 16 Jun 1737 to Lanslott Crost late of Hanover and by Crest sold to Edward Arnold, by Arnold sold to Benjamin Arnold & by sd Benjamin to sd Richard Johnson.
Signed: Richard Johnson
Wit: William Johnson, Richard Johnson, Isham Johnson. Louisa Co DB 3, p.256
Robert Tenham left a will naming his daughter as Sarah Johnson - believed to be the wife of James Johnson, brother of Isham. However, James Johnson was alive and well at the time of this deed so his wife would not be holding title to deeds. John Boswell was executor of Tenham's will in 1763; Boswell was the husband of Richard Johnson's sister Ann. The second Richard, the witness, may be Isham's brother as follows.

I found the patent referred above on the Library of Virginia website. It was issued 16 Jun 1727, not 1737, to Lancelot Crest of Hanover County, for 200 acres; boundary markers described as Clark's corner, Johnson's line and corner, Wm. Alvis's line and corner, Capt. Clark's line.

An Isham Johnson died in Louisa Co in 1766. No wife was named - he named a sister Susannah and two brother, Richard and James. There was little, only two slaves and personal items.
Will of Isham Johnson, to sister Susannah Johnson, wench I hired to Peter Shelton called Phillis; to brother Richard Johnson, negro Sanyo and crop now growing and the money I have by me to James Johnson my brother he paying all my debts. Wit: James Johnson, Richard Johnson Susannah (X) Johnson. Rec. 11 Aug 1766. Lousia Co WB 1, p.84

DB C 1/2, p.171
I Richard Johnson of Louisa Co for me and my heirs release renounce and forever quit Claim unto James Johnson of same Co all benefit, Gift, legacy or bequest whatsoever to me belonging by reason of the will of Isham Johnson, dec'd.
11 Aug 1766. Signed: Richard Johnson.
Acknowledged by Richard on the same day.

Birth

Abt 1732

Father	Johnson ( - )
Sibling	James Johnson (1730 - 1792)
Sibling	Susannah Johnson (1734 - )
Sibling	Richard Johnson (1736 - )