Katherine de St. Pierre was born on an unknown date to Urian de St. Pierre (c1240-1293) and Idonea de Malpas (c1243-1293) . She married Randolph de Thornton (c1254-) . She married William de Venables (-aft1300) .
Katherine, daughter of sir Urian de St. Pierre, widow of sir Randle le Roter of Thornton, living 24 Edw. I. 1296, married 2ndly Sir William de Venables of Bradwell and had William Venables of Bradwall.
--The History of the County Palatine and City of Chester: Comp. from Original Evidences in Public Offices, the Harleian and Cottonian Mss., Parochial Registers, Private Muniments, Unpublished Ms. Collections of Successive Cheshire Antiquaries, and a Personal Survey of Every Township in the County; Incorporated with a Republication of King's Vale Royal and Leycester's Cheshire Antiquities, Volume 1 by George Ormerod, Daniel King, William Smith, William Webb (sheriff.), Sir Peter Leycester
Children
| Name | Birth | Death | Joined with |
| Peter de Thornton (c1290-1358) | 1290 England | 1350 England | Lucia de Hellesby (c1297-1335) |
| Name | Birth | Death | Joined with |
| William Venables | |||
Siblings
| Name | Birth | Death | Joined with |
| Katherine de St. Pierre (c1266-) | Randolph de Thornton (c1254-) William de Venables (-aft1300) | ||
| Joan de St. Pierre (-aft1298) | 1298 England | Hugh de Dutton (-1294) | |