Here’s a better match: Theodore Blethin, b. 14 Mar 1616, bap. 23 Mar 1616, Mathern, Monmouthshire, Wales. Father: Phileman.
Source: Monmouthshire, Wales, Anglican Baptisms, Marriages and Burials, 1551-1994.
And this looks very likely to be his daughter: Anne Blethen, d. 1657, buried 22 Feb 1657, St Andrew’s, Holborn, London. Father: Theorder Blethen.
Source: London, England, Church of England Baptisms, Marriages and Burials 1538-1812 (London Metropolitan Archive).
Alan