Katherine married Sir William ( 3rd Baron Montacute, 1st Earl of Salisbury, and King of Mann) De Montagu in 1327 in Cassington, Oxfordshire, England. Sir (son of William III, (2nd Baron of Salisbury,) DeMontagu (maid. name 1) and ELIZABETH Baroness De MONTFORT (maid. name 1)) was born in 1301 in Salisbury, Wiltshire, England; died on 30 Jan 1334 in killed at tournament windsor Berkshire, England. [Group Sheet] [Family Chart]

1. Elizabeth Montagu (maid. name 1) was born in 1327 in Donyatt, Somerset, England; died on 31 May 1359 in Ashley, Hampshire, England; was buried in Tewkesbury, Tewkesbury Borough, Gloucestershire, England.
2. John (2nd Earl of Salisbury, 4th Baron Montagu) DeMontagu was born in 1327 in , Somerset, , England; died on 25 Feb 1390 in Salisbury Cathedral, Salisbury, Wiltshire, England.
3. Philippe (Philippa) DeMontagu was born in 1332 in Salisbury, Wiltshire, England; died on 5 Jan 1382 in Bur Bisham, Berks, Gland, England.