He was born at Cromwell House in Huntingdon on 25 April 1599,[8] to Robert Cromwell and Elizabeth Steward. He was descended from Katherine Cromwell (born c. 1482), an elder sister of Tudor statesman Thomas Cromwell (c. 1485–1540), a minister of Henry VIII, whose family acquired considerable wealth by taking over monastery property during the Reformation. Katherine was married to Morgan ap William, son of William ap Yevan of Wales. The family line continued through Richard Williams, alias Cromwell, (c. 1500–1544), Henry Williams, alias Cromwell, (c. 1524–6 January 1604),[9] then to Oliver's father Robert Cromwell (c. 1560–1617), who married Elizabeth Steward (c. 1564–1654) on the day of Oliver Cromwell's birth. Thomas thus was Oliver's great-great-great-uncle.[10]

At the time of his birth his grandfather, Sir Henry Williams, was one of the two wealthiest landowners in Huntingdonshire. Cromwell's father Robert was of modest means but still inside the gentry class. As a younger son with many siblings, Robert's inheritance was limited to a house at Huntingdon and a small amount of land. This land would have generated an income of up to £300 a year, near the bottom of the range of gentry incomes.[11] Cromwell himself in 1654 said "I was by birth a gentleman, living neither in considerable height, nor yet in obscurity".[12]
Records survive of Cromwell's baptism on 29 April 1599 at St. John's Church,[13] and his attendance at Huntingdon Grammar School. He went on to study at Sidney Sussex College, Cambridge, which was then a recently founded college with a strong Puritan ethos. He left in June 1617 without taking a degree, immediately after the death of his father.[14] Early biographers claim he then attended Lincoln's Inn, but there is no record of him in the Inn's archives. Fraser (1973) concludes he likely did train at one of the London Inns of Court during this time. His grandfather, his father, and two of his uncles had attended Lincoln's Inn, and Cromwell sent his son Richard there in 1647.[15]
Cromwell probably returned home to Huntingdon after his father's death, for his mother was widowed and his seven sisters were unmarried, and he, therefore, was needed at home to help his family.[16]

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