He was the son of Sir Robert Harington (d1334), who predeceased his own father the 1st Baron. His mother was Elizabeth de Multon (born 1306), daughter of Thomas de Multon and one of the three sisters and co-heiresses of John de Multon. She was the heiress of several estates including: Thurston in Suffolk.
Moulton, Skirbeck and Fleet in Lincolnshire, of Egremont in Cumbria and of manors in County Limerick, Ireland.
Elizabeth outlived her husband and in about 1334 remarried to Walter de Birmingham.