According to Ella Hazel Atterbury Spraker's book on "The Boone Family," pages 591-593, John Webb married Mary Boone, daughter of George Boone and Mary Maugridge and sister of Squire Boone, Sr.I believe she cites Gwynedd Monthly Meeting records for their engagement on 26 July 1720 and marriage on 13 September 1720.
Spraker at page 596 quotes Exeter Monthly Meeting records (Exeter, PA) for birth dates of the children of John and Mary (Boone) Webb.Sarah's birth is reported to have been on "8 mo. 17, 1729."That might be August 17 or October 17, depending on whether it was Julian or Gregorian calendar, which isn't always clear with Quaker records.
Is your son-in-law related to the famous Bill "Cuffs" Caudill, the long-ago closer for the Seattle Mariners?