So you have John born 1730 & marrying in 1737?....Something not adding up with your dates on this lot?
John Keen married Margaret Isles, 26 Feb 1753, Preshute, Wiltshire. Both of Wanborough.
Son Thomas bap. 28 November 1754, Wanborough. Died of smallpox, and buried 15 January 1817, Chiseldon.
It does rather look as though Sylvester called himself John for some unknown reason when he married Alethea in Great Faringdon in 1729. Family Search entry from microfilm 88260, Parish Registers of Great Faringdon - baptisms, marriages and burials, 1653-1812.
Licence, dated one day before the marriage, apparently says that "John" was of Swindon, a barber?, Alethea was a spinster of Chiseldon.
Wasn't Sylvester Keen buried at Swindon Holy Rood? He is at least on a MI there (1745)
Along with parents Mary (1681-1753) and John.
Sylvester was "that friend of the Devil", the Swindon bailiff?
If Alethia did not remarry she might be buried in Chiseldon. I mean, maybe she is the unnamed Keene buried there 1797 age 91. Info from transcripts. Perhaps its Widow Keene or similar, although it could be a male of course.
Or was Sylvester's father John buried in Iron Acton, and his wife and son in Swindon? Is this the will you refer to?
PCC Will of John Keen or Keene, Yeoman of Iron Acton, Gloucestershire, 15 July 1719 (PROB 11/569/318)
Chancery Case, Keen v Keen ?, you would really need to try to get to see it at the National Archives
C 11/665/34
Short title: Kenn v Keen
Bill and answer.
Plaintiffs: Richard Keen and Wayte Keen (two sons of John Keen, yeoman deceased, late of Latteridge, Iron Acton, Gloucestershire), infants (by Thomas Waite, gent of Swindon, Wiltshire).
Defendants: Silvester Keen, Noblet Ruddock, Thomas Shute, John Ridley, Dame Mary Whetstone, Thomas Yate, James Donning and John Samson.
Date of bill (or first document): 1720