He is married to Marie de Nesle.
They got married
Child(ren):
JEAN de Looz, son of JEAN [I] Comte de Looz et de Chiny & his second wife Isabelle de Condé (-Brescia [1310/11]). "Nichols de Condeit Seigneur de Moriames" recorded disputes between "Arnous Cuens de Los" and "madame Isabeau masseur et Jean et Jacquemin ses fils" and that "Arnous" had granted his possessions "en la terre de Warc, Agimont et Givet" to "Jean et Jacquemin ses freres enfans susdite" in return for their renunciation of claims "en la comté de Los", by charter dated Apr 1280[878]. Seigneur d’Agimont.
[m firstly ---. This first marriage is suggested because of the possible birth date of Jean’s oldest son Jean, which indicates that he was probably much older than his three siblings. Bearing in mind that Jean de Looz-Agimont’s known wife Marie de Nesle had children by her second marriage, it is possible that she was not the mother of her husband’s oldest son.]
m [secondly] [as her first husband,] MARIE de Nesle Dame de Warcq et de Gernomont, daughter of JEAN [II] de Nesle Seigneur de Falvy & his wife Marie van Oudenaarde (-after 1328). Père Anselme (naming her “Marguerite”) records her parentage and marriage without citing any source on which he bases the information[879]. The primary source which confirms this information has not been identified. [She may have married secondly (after [1310/11]) Aubert [III] Seigneur de Longueval: According to Goethals, Aubert [III] de Longueval married “Marie de Neelle, fille de Jean de Neelle seigneur de Faluy et de Herelle et de Mari d’Audenarde [qui] venait de perdre son mari Jean de Los seigneur d’Agimont [mort] en Italie en 1310” and by her had three children[880]. The primary source which confirms this information has not been identified. From a chronological point of view, it appears possible so long as Marie was one of her parents’ younger children.]
Jean [I] & his [first/second] wife had one child:
JEAN [II] de Looz ([before 1290?]-before 28 Dec 1323)
Jean [I] & his [second] wife had four children:
LOUIS de Looz dit d´Agimont (-1345 or after)
ARNAUD de Looz (-before 2 Sep 1373).
JEAN de Looz ([1305/10?]-after 1340).
MARGUERITE de Looz (-bur Braine-l’Alleud).
Bronnen:
[878] Butkens (1724), Vol. I, Preuves, p. 114, "Extraict des registres de S. Lambert à Liege".
[879] Père Anselme, Tome II, p. 334.
[880] Goethals, F. V. (1862) Miroir des notabilités nobiliaires de Belgique, des Pays-Bas et du Nord de la France (Brussels), Tome II, p. 794, no citation reference.
https://fmg.ac/Projects/MedLands/LOTHARINGIAN%20(LOWER)%20NOBILITY.htm#JeanLoozdied1311