Thomas de Willoughby , of Mumby, Sir
Thomas de was born about 1268 in Willoughby with Sloothby, Spilsby, Lincolnshire, England.  He died after 1300 in Mumby, Spilsby, Lincolnshire, England.

 Margaret Heiress de Mumby
Margaret Heiress de was born about 1270 in Mumby, Spilsby, Lincolnshire, England.  Margaret Heiress de is no longer alive.

 Agnes de Willoughby
Agnes de was born about 1296 in Mumby, Spilsby, Lincolnshire, England.