Parents of Maria Angelina are known from her marriage licenses, issued in 1253 and 1254 by the papal chancellery. The first mentions the marriage ""inter Anselmum de Keu ac Mariam, natam Matildis dominae de Posaga, natae comitissae Viennensis"", while the second mentions ""Maria, nate quondam Calojohanni"" and also mentions Maria′s maternal uncle as ""imperatore Constantinopolitano, eiusdem Matildis avunculo"". Those data allowed McDaniel to identify Maria′s father as John Angelos, lord of Syrmia, and Maria′s mother as Matilda, daughter of Henry I, Count of Vianden and Margaret Courtenay (sister of the Latin emperors Robert and Baldwin II).