'Castle, Henry. ... The first six children of Henry and Abigail were bapt. together at Woodbury, Sept. 1686, and we assume that the mother was Abigail Dickerson. ... Ages of children [in Feb. 1697/8]: Henry 31, Samuel 29, Isaac 25, William 10, Abigail 22, Mary 20, Mercy 13.'
His birth date and christening date are both given as 6 Sep 1672, in Woodbury.
His birth is not listed in the Woodbury VRs (Barbour Collection) (or Fairfield or Stratford - other alternatives given by other compilers), and he was baptized in 1686, at the age of 14. It appears that there is no primary source to support his birth date. The births of his siblings do not appear to have been recorded in public records, so there is no reason to believe that his was recorded either, although it is possible that his birth date was originally taken from a family record.
'Children [of Henry Castle], bapt. at Woodbury: ... Isaac, b. abt. 1672, d. 25 July 1727; m. (1) Sarah Adams, dau. of Samuel of Fairfield, b.3 Oct. 1680, d. at Woodbury, 24 Feb. 1707/8; m. (2) abt. 1716, Joanna -----.'