Edward Glascock, [matric. Cambridge 1638]

From this document from Christ's College, Cambridge, we can determine that Margery Fitch, sister of William, was married to Henry Glascock of Hartesbury in Essex who matriculated Christ's College in 1581 (placing his birth approximately at 1560), and that their grandchildren included William Glascock matriculated 1626 (so perhaps born betw. 1605-1609) and a younger brother Edward (admitted in 1638, so perhaps born c 1618). William married Elizabeth Skiers of Slyfied Surrey and had sons Ignatius, William, and (probably) Richard.

Biographical Register of Christ's College, 1505-1905, (Google Books)

p. 167:

Henry Glascock: mat. pen. 1581 Nov, Probably BA (Clare H.) 1585 June 11; MA 1589. Author of verses in the University Collection on the death of Sir Philip Sidney 1587 (Ath Cant 286). Perhaps son of John of High Easter, Essex who married Grace Ennew of Coggheshall (Essex Visitations 1634). Grandfather of William (adm 1627) and of Edward (adm 1638).

p. 388 :

William Glascock, matriculated pensioner 17 March 1626/7; BA 1629/30. Admitted at Gray's Inn as "son and heir of Henry Glascock of Hartisowberrie, Essex" 7 Feb 1630/31. Eldest son of Henry [matric. Christ's 1581] of "Hartishobury" (Hartesbury) of Farnham, Essex, and of Margery, sister of Sir. Will. Fitch. Elder brother of Edward (adm'd 1638). Married Elizabeth, dau of George Skiers of Slyfield, Surrey, and had sons Ignatius and William, perhaps also Richard (adm'd 1654/5). Essex Visit. 1664-8.