William Willoughby, 3rd Baron Willoughby of Parham, was born 1584 in Knaith, Lincolnshire, England, United Kingdom to William Willoughby (1561-1601) and Elizabeth Hildyard (c1558-1601) and died 28 August 1617 Knaith, Lincolnshire, England, United Kingdom of unspecified causes. He married Frances Manners (1588-1643) 4 February 1603 .
|Offspring of William Willoughby, 3rd Baron Willoughby of Parham and Frances Manners (1588-1643)|
|Henry Willoughby, 4th Baron Willoughby (c1612-c1618)|
|Francis Willoughby, 5th Baron Willoughby (1614-1666)||1614||23 July 1666||Elizabeth Cecil (c1606-1661)|
|Frances Willoughby (1614-1649)|
|William Willoughby, 6th Baron Willoughby (1616-1673)|