He was the son of Edward Winslow and Magdalene Ollyver. He was the brother of Gov. Edward Winslow "Mayflower Passenger" 
Josiah Winslow was baptized 16 Feb 1605/6.
He is buried at Old Winslow Burying Ground, Marshfield, Plymouth, MA - he is memorialized as one of the first settlers of Marshfield on cenotaph at Old Winslow Cem
Josiah Winslow's Will and Death
Josiah Winslow's confusion over financial matters apparently held to the last, and the court made void his conditional bequest of house and land to his son Jonathan, as he had already given the property to him at his marriage. On 1 Mar 1674/75 the court ruled that because he had during his life already given his lands in Marshfield without restriction to his son Jonathan on the latter’s marriage to Ruth, the daughter of Mr. William Sergeant, but in his will left the same lands to Jonathan in fee tail (which basically meant that he could not sell them), that part of the will was void, but the rest would stand 
The New England Historical & Genealogical Register, 1847-2011
U.S. and Canada, Passenger and Immigration Lists Index, 1500s-1900s
U.S. and International Marriage Records, 1560-1900
Marshfield, 70 - 40'W by 42 - 5'N: The Autobiography of a Pilgrim Town, 1640-1940 copyright 1940 by Marshfield Tercentenary Committee, published by The Rapid Service Press. Josiah mentioned on pp. 7, 12, 51 & 73.
Memorials of Marshfield and Guide Book to Its Localities at Green Harbor copyright 1854 by Marcia A. Thomas. Published by Dutton and Wentworth, 37 Congress Street, Boston, MA 
Vital Records of Marshfield, Massachusetts, to 1850 copyright 1969 by Society of Mayflower Descendants in the State of Rhode Island "to commemorate the 350th Anniversary of the Landing of the Pilgrims 1970." Compiled by Robert M. Sherman and Ruth Wilder Sherman. ISBN: 0-930272-03-8
Added image of pages 28 and 29 of the book Memorials of Marshfield and Guide Book to Its Localities at Green Harbor by Marcia A. Thomas, copyright 1854 by Dutton & Wentworth, Boston. Contains same info as Anderson's Great Migration without the copyright problem.