ARGUERITE [Sibylle] de Courtenay ([1194]-Marienthal convent 17 Jul 1270, bur Marienthal). The Chronicle of Alberic de Trois-Fontaines names "secundam filiarum eius [Namucensis comitis Petri] Sibiliam" as the wife firstly of "Radulfus de Essolduno in Bituria" and secondly of "comes Heinricus de Vienne et Ardenna". He also cites her supposed third marriage to "Lascarus Grecus…imperator Nicee", but is here confusing her with her younger sister Marie[54]. "Radulphus dominus Exolduni" sold land at Germigny to Eudes Duke of Burgundy, with the consent of "Margarita uxore mea", by charter dated 1210[55]. She succeeded her first husband in 1216 as Dame de Châteauneuf-sur-Cher et de Mareuil-en-Berry. She took possession of Namur as Marquise de Namur in 1229 on the death of her brother Henri. The Chronicle of Alberic de Trois-Fontaines records that, on the death in 1229 of "comite Namucensi Henrici puero", his sister "Sibilia comitissa Vienne" occupied "castrum Namuci" against the competing claim of Fernando Count of Flanders[56]. "Henricus marchio Namucensis et Viennæ comes et Margarita marcionissa et comitissa uxor eius" confirmed the foundation of the abbey of Grandpré by "prædecessoris ac fratris nostri Philippi bonæ memoriæ" by charter dated Aug 1231[57]. She was obliged to transfer Namur to her brother Baudouin in 1237. "Henricus et Margarita comitissa Viennensis" founded a monastery at Vianden, with the consent of "Philippi nostri primogeniti", as well as anniversaries for themselves "et filiorum nostrorum…Friderici et Philippi", by charter dated Jun 1248[58]. She became a nun at the convent of Marienthal near Luxembourg after the death of her second husband[59]. m firstly ([1210]) RAOUL [III] Sire d'Issoudun, son of EUDES [III] Sire d'Issoudun & his wife Alix de Montbard (-1 Mar 1212). m secondly (1216) HEINRICH [I] Graf von Vianden, son of FRIEDRICH [III] Graf von Vianden & his wife Mechtild von der Neuerburg (-Palestine 19 Nov 1253[60]). He succeeded as Marquis de Namur from 1229 to 1237, by right of his wife.