THIERRY de Mousson, son of LOUIS Comte de Mousson & his wife Sophie of Upper Lotharingia ([1045]-1/2 Jan 1103, bur Autun Cathedral). The Chronicle of Alberic de Trois-Fontaines names "Theodericum" as son of "comiti Montionis Ludovico" and his wife Sophie[68]. "Filia Wilelmi comitis de Burgundia Hermentrudis…" founded the Cluniac abbey of Froidefontaine by charter dated 8 Mar 1105 in which she names "suis antecessoribus…Lodewico, Sophia eius uxore, et filiis eorum Brunone, Theoderico, Lodewico, Friderico, filiabus vero Mathilde, Sophia, Beatrice…"[69]. On his marriage, he entered into possession of the château and seigneurie de Montbéliard[70]. He succeeded his father in [1071/76] in his territories of Altkirch, Ferrette, and around Hagenau. He was present at the 1076 enfranchisement of the chapel in the castle of Amance[71]. He inherited the region of the future county of Bar from his mother in 1093. He had taken a vow to join the First Crusade but was released from it due to illness. He was invested as Comte de Verdun after 1096 by Richer Bishop of Verdun[72]. He dictated his testament in 1102 at the castle of Altkirch[73]. The Obituaire de Saint-Mansuy-lès-Toul records the death "1 Jan" of "Henricus et Theodoricus comites"[74].
m ([1065]) ERMENTRUDE de Bourgogne heiress of Montbéliard, daughter of GUILLAUME I "le Grand" Comte Palatin de Bourgogne & his wife Etiennette --- ([1050/55][75]-1106 or after, bur Autun Cathedral). The Chronicle of Alberic de Trois-Fontainesnames "Ermentrudem"as wife of "Theodericum [filiuscomiti Montionis Ludovico]" specifying that she was heiress to Montbéliard[76]. "Filia Wilelmi comitis de Burgundia Hermentrudis et filii sui Fridericus, Raginaudus, Theodericus" founded the Cluniac abbey of Froidefontaine by charter dated 8 Mar 1105 in which she names "suis antecessoribus…Lodewico, Sophia eius uxore, et filiis eorum Brunone, Theoderico, Lodewico, Friderico, filiabus vero Mathilde, Sophia, Beatrice, filiis autem Theoderici atque sue uxoris Hermentrudis, Lodewico, Wilelmo, Hugone", witnessed by "Henricus de Suarca cum genero suo Gerunch, Gotefridus filius avunculi eiusdem comitis [Friderici]"[77]. It is assumedfrom the expression "suis antecessoribus" that all those so described were deceased at the date of the foundation. She subscribed her son Renaud's act of sale of the fortress of Commercy to the abbé de Saint-Mihiel in 1106[78].
Comte Thierry & his wife had ten children