From the Celtic Casimir online family tree:

http://www.celtic-casimir.com/webtree/15/31463.htm

Lucy DE BRUS 593,8309,8310

Born: Abt 1234, Skelton Castle, Yorkshire, England

Died: After Apr 1282 8309

General Notes:

He [Marmaduke de Thweng] married, about 1242, Lucy, 2nd daughter of Piers DE BRUS, lord of Skelton, Yorks, by Hawise, sister and coh. of William DE LANCASTER (died 1246), lord of Kendal, Westmorland. He died 1282-1284 (b). Lucy was living, Easter, 1282. [Complete Peerage XII/1:738-9, XIV:612, (transcribed by Dave Utzinger)] 593

Marriage Information:

Lucy married Sir Marmaduke DE THWENG Lord Kilton, M.P., son of Sir Robert DE THWENG Lord of Kilton and Maud DE KILTON Heiress. (Sir Marmaduke DE THWENG Lord Kilton, M.P. was born about 1234 in Kilton Castle, Cleveland, Yorkshire, England 7404 and died between 1282 and 1284 in Castleton Castle, Derbyshire, England 7404.)

-------------------- daughter of Peter Brus of Skelton and Helwise Merley de Lancaster fitzGerald. disconnected from Robert de Brus of Scotland and Annandale.