Little is currently documented about John Nixon, second husband of Em (Unknown) Pike Nixon Mayo. While there is no reason to believe the limited extant colonial records are for two men of the same name, we do not know that they are the same man.
A possible marriage record is found in London 1683 which date would work with the 1681 death date of Em's first husband John Pike. But, other than similarity of name, we cannot yet be certain this is the marriage of this John "Nickson" and Em Pike.
Asking for any assistance and insight from England project and US Southern Colonies project members to see if additional relevant records can be located. I have found nothing further at Colonial and State Records of North Carolina.