William Brewster was born about 1564, most probably in Scrooby, Nottinghamshire, England.
He was the son of William Brewster and Mary (Smythe) (Simkinson) Brewster and he had a number of siblings, including James, Prudence, Henry, George, and Edward Brewster.
His paternal grandparents were William Brewster (1510–1558), and Maud Mann (1513–1558), from Scotland.
Their other children were: Fear, [vicar) Henry, Prudence and Thomas Brewster.

Beginning in 1580, he studied briefly at Peterhouse, Cambridge, before entering the service of William Davison, ambassador to the Netherlands, in 1584, giving him opportunity to hear and see more of reformed religion.
Brewster was the only Pilgrim with political and diplomatic experience.
With his mentor in prison, Brewster had returned home to Scrooby for a time, where he took up his father's former position as postmaster in 1590.
The historian Stephen Tomkins argues that William and Mary became puritans in the mid/late 1590s, judging by the names of their children, which became much more puritan after Jonathan.
It appears their daughter Fear, born about 1606, was named after her great-aunt Fear Brewster, who died unmarried about two years after William's daughter Fear was born.
 
Following the campaign led by Archbishop Bancroft to force puritan ministers out of the Church of England, the Brewsters joined the Brownist church led by John Robinson and Richard Clifton, inviting them to meet in their manor house in Scrooby.
Restrictions and pressures applied by the authorities convinced the congregation of a need to emigrate to the more sympathetic atmosphere of Holland, and Brewster organised the removal.
Leaving England without permission was illegal at the time, so that departure was a complex matter.
On its first attempt, in 1607, the group was arrested at Scotia Creek, but in 1608, Brewster and others were successful in leaving from The Humber.
William Brewster was born about 1564, most probably in Scrooby, Nottinghamshire, England. He was the son of William Brewster and Mary (Smythe) (Simkinson) Brewster and he had a number of siblings, including James, Prudence, Henry, George, and Edward Brewster. His paternal grandparents were William Brewster (1510–1558), and Maud Mann (1513–1558), from Scotland. Their other children were: Fear, [vicar) Henry, Prudence and Thomas Brewster.
Beginning in 1580, he studied briefly at Peterhouse, Cambridge, before entering the service of William Davison, ambassador to the Netherlands, in 1584, giving him opportunity to hear and see more of reformed religion. Brewster was the only Pilgrim with political and diplomatic experience. With his mentor in prison, Brewster had returned home to Scrooby for a time, where he took up his father's former position as postmaster in 1590. The historian Stephen Tomkins argues that William and Mary became puritans in the mid/late 1590s, judging by the names of their children, which became much more puritan after Jonathan. It appears their daughter Fear, born about 1606, was named after her great-aunt Fear Brewster, who died unmarried about two years after William's daughter Fear was born.  
Following the campaign led by Archbishop Bancroft to force puritan ministers out of the Church of England, the Brewsters joined the Brownist church led by John Robinson and Richard Clifton, inviting them to meet in their manor house in Scrooby. Restrictions and pressures applied by the authorities convinced the congregation of a need to emigrate to the more sympathetic atmosphere of Holland, and Brewster organised the removal. Leaving England without permission was illegal at the time, so that departure was a complex matter. On its first attempt, in 1607, the group was arrested at Scotia Creek, but in 1608, Brewster and others were successful in leaving from The Humber.
William Brewster (Mayflower passenger)