It is certain that Martha King Britt was the mother of Blackman, Pashann (Patience?), Henry, and possibly some other children.
Martha King Britt, wife of Thomas Britt, is named in her father or mother's will (I cannot remember which one) -- Martha was the daughter of William King of Bertie County who was a descendent of Michael King of Nansemond County, VA.
Three of Blackmon Britts' daughters married three King brothers in the area around Grantham (Wayne County). It is not very far from Bentonville. The men they married were related somehow to Martha King Britt, possibly distant cousins.
Thomas and Martha Britt first show up in the 1840 Johnston County Census. I am not sure but I think I could not locate them in Bertie County in 1820 or 1830. I am just wondering if Thomas went to Wayne County or Sampson, and then ended up in Johnston in 1840. Everything that I have seen by people says that all of the children were born in Bertie County, but I am not so sure. Martha King Britt probably died after 1815 (Pashann b. 1812, Blackman b. 1813, and Henry b. 1815) and then there are 9 children born between 1825 and 1845. Some were most assuredly born in Johnston County, but where were the rest born?
I am just wondering if his second wife was named Martha Ridgon or else Martha Jenkins. I have found the surname of Ridgon in Bertie County. Martha King Britt also had a first cousin named Martha, referred to as Patsy Ann (she was the daughter of Charles King, William's brother). I believe (not certain) that she married a Rigdon Jenkins in Bertie County.
Does your brother-in-law have anyone in his family who can shed some light on this matter?
My research indicates that Thomas served in the War of 1812.