Upon his father's death in 1594, most of the family estates, in Wiltshire, went to his elder brother Walter; John received the manor of Garsington, Oxfordshire, and was promised £200 when he came of age.
[2] Sir Oliver arranged for John's education: he matriculated at Trinity College, Oxford, on 3 April 1601 and was admitted to Lincoln's Inn in 1604.
[1] Meanwhile, John's brother Walter drowned near Castle Cornet in August 1597 while staying with Sir Thomas Leighton, Governor of Guernsey.
His mother died in 1598, leaving him her jointure estates of Purley Park, Berkshire, and Hatfield Peverel, Essex.
Sir Thomas Leighton purchased his wardship in 1602, and received permission to settle various estates on his daughter Anne, who married St John on 9 July 1604 at the age of 12.