Reed, Paul C, Descent of St Maur Family of co Monmouth and Seymour Family of Hatch, co Somerset, in Foundations for Medieval Genealogy, vol 2 no 6 (2008), pp390-442. Available at https://fmg.ac/publications/journal/volume-2/file/256-seymour-1. Information from this source tagged as [Ref: Reed StMAUR p[0-9]*].
Sources for birth and parent Information
father:
[Ref: Reed StMAUR p420]
Sources with Information about marriage to Adam AP CYNHAETHWY