See the Appendix of this article for the evidence for 2 couples named John and Margaret Jarman. In particular (p. 252) 'On 18 4m [June] 1692, the marriage of Rees Thomas and Margaret Aubery was witnessed by persons named John Jarman and John Jarman, Jr.'
Note that Jr. doesn't necessarily mean that the younger John was the son of the older John (or of any other John Jarman). It simply means that he was the younger of 2 men with the same name in the same place. However, a note added to a Find A Grave entry says that someone who claims to be a descendant of Elizabeth Jerman b 1690 (daughter of this John Jarman) has DNA matches to the descendants of several children of Squire Boone and Sarah Morgan, the latter of whom is thought to be a descendant of the older John Jarman.