John Spencer of South Mylls, the son of Robert Spencer of South Mylls and unknown mother, was married to Christian daughter of .... Baker, and had three sons:
1. William Spencer of South Mylls and Meyrs Ashby in Northamptonshire married Issabell Osborne, dau of Edward Osborne of Kenolmarsh, Northamptonshire.
2. Robert Spencer of St Albans Hertfordshire (1572 - Harl MS5867) married Frances dau of John Forster of Branffeld Hertfordshire and had two children - John 10 yrs old in 1572 ob 6 Jan 1622 s.p. marr Margaret Bayly, and Anne wife of ... Gylman
The Visitation of Hertfordshire 1572 shows the same family with basically the same information other than it shows a fourth son, also named Robert, married to .... dau of .... Smyth of Co Bedford The informant was John's son Robert, who should have known if he had a brother also named Robert, but as there's no mention of a second Robert in John's will I have doubts. Or had he died s.p. before 1584?
Neither Visitation shows his daughter Ann (Barnwell), who is a legatee in John's will, and who is also mentioned in her brother Robert's 1584 will. Nor do they show a daughter who married Reynold Basse, again mentioned in Robert's will
He married Etheldreda Vaughan, daughter of .... Coker of Mappowder, Dorset, widow of Richard Watkyns Vaughan, at some between Apr 1550 when her first husband died, and 1551 when he and Etheldreda were plaintiffs in a Chancery Court case (C 1/1270/83), date 1544-1551. 
He and Etheldreda had no children.
His will is dated 20 Dec 1560, probated on 24 Nov 1568. As the will names his son Robert's wife Frances who didn't marry until 1561, and their two children born 1562 and later, the date looks incomplete "a thousand five hundred three score" followed by " ~~ ", as though the scribe knew there was a word missing, eg "seven", or possibly the last word was illegible and he didn't transcribe it.
The will of John Spencer late of Southmylles requested that he be buried in Blunham next to the body of his late wife Etheldrede.
The lengthy will also mentions:
my gentle and good brother Sir John Baker, priest ie ? his brother in law? Brother of his first wife Christian Baker perhaps?
my son William Spencer
my son Robert Spencer he didn't marry Frances Foster until 1561
Robert's daughter Ann Spencer (unmarried)
his chamber at Bramfield
Robert's son John Spencer who wasn't born until 1562
my son John Spencer of London
John's dau Elizabeth
my daughter Ann Barnwell m Edward Barnwell of Cransley, Norfolk
my daughter in law Jane Fysher? he uses "daughter" for "daughter in law". I=Does he use daughter in law for step daughter?
my ?noste? Coke of London (is this Coker, his second wife's maiden name?)
my daughter Frances Spencer ie daughter in law
my daughter, William Spencer's wife ie daughter in law
my son John Spencer's wife
He acquired the manor of Bramfield in 1565 after his son Robert had married the daughter of the previous owner. It was was alienated to John Forster and Margery his wife in 1557/8. On his death in February, 1559, Forster bequeathed the manor of Bramfield to his wife for the term of her life, with remainder to his son Humphrey, and in 1565 Humphrey conveyed it to John Spencer, gentleman. (Humphrey's sister Frances was married to John's son Robert). John Spencer, citizen and grocer of London, and George Smyth sold it in 1567. It seems that John the father acquired the property in 1565, and on his death in 1567 it was sold by his son, John the grocer.