A 1616 pedigree of the Knightley family states, "Robertus de Plumpton, miles, Dominus de Plumpton, in comitatu Nortampton = Alicia, filia Roberti Wandard, Dominus de Mollingten, in com. Oxon." and shows Robert as the son of "Robertus de Plumpton, frater et heres Willielmi de Plumpton, dominus manerii de Plumpton. Azure five fusils in fess or, each charged with a mullet gules. The pedigree shows Robert and Alice as the parents of Sara who married William St. John. [1]
[1] Joseph Jackson Howard, ed., "Pedigree of the Knightley Family of Fawsley, Co. Northampton, compiled by Augustine Vincent, from the original in the possession of Sir R. Knightley, Bart., M.P.," Miscellanea Genealogica et Heraldica, Vol. 1 (London: Hamilton, Adams, and Co., 1868), 88-102 at 91-92, [GoogleBooks], [HathiTrust].