John below links to the wider tree in the 1635 Visitation and also Darlene's link above.
Venn (Alumni Cantabrigiensis) which I know you have already looked at has several Clarkes from Stevenage as well as those from Bennington/Walkern . All but one went to the same college (Caius and Gonville) http://venn.lib.cam.ac.uk/acad/2016/search-2016.html
Starting from that I compiled an outline list which absolutely needs double checking as I have amended things several times
A History of Gonville and Keyes College pub 1849-1897 also by Venn frequently gives more detail but some may be very speculative (link below)
John of Stevenage father of
John (b. c. 1550?) BA Christs 1571, ordained 1573, MA Caius 1574, One of name became Rector of Walkern 1604, death 1612, will proved 1613
See also. http://db.theclergydatabase.org.uk/jsp/persons/CreatePersonFrames.jsp?PersonID=138911
History of Caius
https://archive.org/stream/biographicalhist01venn#page/70/mode/2up
TNA PROB 11/122/159 Will of John Clark, Clerk of Walkern, Hertfordshire Date: 23 August 1613
He was father of Robert, Phillip,(another one!) Beatrice(she under 21 at time will written), husband of Alice
Thomas of Stevenage, described in one entry of 'Alumuni' as gent and 'History of Caius' as of mediocris fortunae
father of
William, b. c.1552,school Eton (Eaton Socon? ), P 72 hist of Caius
Edward,b.c. 1558, p.78, hist of Caius
Christopher b.c. 1561, Stevenage, P 91 hist of Caius
Francis, born Eaton Socon Beds, b.c.1563 hist of Caius p 91(he is Francis 'of Houghton and was knted 1624 and is on 1635 Herts visitation and also the 1624 Vist of London)
William of Bennington, mediocris fortunae, father of
George b.c. 1553, " A ‘George Clarke, of Linc. Diocese’subscribed for priest’s orders (Linc.) Ap. 8 1578. Perhaps the rector of Monks Risborough, Bucks., who had a license to marry Elizabeth Gouldwell,of Duxford, 15S4 (Ely Marr. Lic.). Rector of Scampton, 1587; and of Kirkby on Bain, 1597; both in Lincs" Hist of Caius p 70
John b.c. 1557 poss later adm Gray's Inn hist of Caius p 72
George of Bennington, Barrister ?? Father of
John born Hitcham, Bucks b.c 1556 (adm Kings) (This one is only a suggested as a possibility in Venn. Alumin No trace found as yet, see below.)
John of Stevenage, yeoman father of
Edward, b.c. 1575 (adm Cauis) Hist of Caius P142, ordained, worked in Ireland, left will prob 1640 in Dublin "He seems to have been a nephew of Sir Francis Clarke 1577 (v London Visitation 1633) "
Notes on Hitcham
Have followed up in quite a bit of detail, found no link yet though the line does go back to a Sir John Clarke of Weston d 1539, http://www.mbs-brasses.co.uk/page113.html
Vic County History for Hitcham has some info (Sir John Clarke of Weston father of Nicholas Clarke d 1551, father of Sir William Clarke born before 1550 who had five sons including William (MP), Hercules and Sir Francis, bur Hitcham 1631 ). I haven't found a George but not found all names of sons.