He was the great-grandson of Christopher St. John, Esquire (1547–1616), Lord of Uchel-olau until his death, and his wife Elizabeth Bawdrip.
This St. John family came from a small, now abandoned, feudal village called Uchel-olau (High-light in English), Glamorganshire, Wales.
Matthias and his uncle Matthew have been merged into 1 person in the 1907 St. John Genealogy book.
On one occasion, he was brought before the court accused of selling "syder to Indians by which they was Drunke" [sic].
In 1657, he is recorded as working with Isacke More, and Edward Nash to "make and provide a good and sufficient wolfe-pit."
[sic] The record states that Matthias was chosen in 1660, as a townsman "to act and agitate all such affairs and occasions as the orders of the court authoriseth and that for the Yere ensuinge."