Niece of Emperor Henry III (Williamson, David. Debrett's kings and queens of Britain. Topsfield, Mass. : Salem House Publishers, 1969, pg. 219). Of Germany (Browning, Charles H. Americans of royal descent, 7th ed. Baltimore : Genealogical Pub. Co., 1986, pg. 282). WWW site directory of royal genealogy lists several possibilities for her parents. See note under husband Edward.
Nothing is known of Agatha's early life, and what speculation has appeared is inextricably linked to the contentious issue of Agatha's paternity, one of the unresolved questions of medieval genealogy. As the birth of her children is speculatively placed at around the year 1045, her own birth was probably before about 1030. She came to England with her husband and children in 1057, but was widowed shortly after her arrival. Following the Norman conquest of England, in 1067 she fled with her children to Scotland, finding refuge under her future son-in-law Malcolm III. While one modern source indicates that she spent her last years as a nun at Newcastle-upon-Tyne, dying before about 1093, Simeon of Durham carries what appears to be the last reference to her in 1070.
Agatha's origin is alluded to in numerous surviving medieval sources, but the information they provide is sometimes imprecise, often contradictory, and occasionally cannot possibly be correct. The earliest surviving source, the Anglo-Saxon Chronicle, along with Florence of Worcester's Chronicon ex chronicis and Regalis prosapia Anglorum, Simeon of Durham and Ailred of Rievaulx describe Agatha as a kinswoman of "Emperor Henry" (thaes ceseres maga, filia germani imperatoris Henrici). In an earlier entry, the same Ailred of Rievaulx had called her a daughter of emperor Henry, as do later sources of dubious credibility such as the Chronicle of Melrose Abbey, while Matthew of Paris calls her the emperor's sister (soror Henrici imperatoris Romani). Geoffrey Gaimar in Lestoire des Engles states that she was daughter of the Hungarian king and queen (Li reis sa fille), although he places the marriage at a time when Edward is thought still to have been in Kiev, while Orderic Vitalis in Historiae Ecclesiasticae is more specific, naming her father as king Solomon (filiam Salomonis Regis Hunorum), actually a contemporary of Agatha's children. William of Malmesbury in De Gestis Regis Anglorum states that Agatha's sister was a Queen of Hungary (reginae sororem) and is echoed in this by Alberic of Trois-Fontaines, while, less precisely, Ailred says of Margaret that she was derived from English and Hungarian royal blood (de semine regio Anglorum et Hungariorum extitit oriunda). Finally, Roger of Howden and the anonymous Leges Edwardi Confessoris indicate that while Edward was a guest of Kievan "king Malesclodus" he married a woman of noble birth (nobili progenio), Leges adding that the mother of St Margaret was of Rus royal blood (ex genere et sanguine regum Rugorum).
Saint Margaret of Scotland, whose name has been highlighted as a clue to her mother Agatha's Eastern origin.
Onomastic analysis has also been brought to bear on the question. The name Agatha itself is rare in western Europe at this time. Likewise, those of her children and grandchildren are either drawn from the pool of Anglo-Saxon names to be expected given her husband's membership of the royal family of Wessex, or else are names not typical of western Europe. There is speculation that those of the latter kind derive from Agatha's eastern European ancestry. Specifically, her own name, the names of her daughters Cristina and Margaret, and those of her grandchildren Alexander, David, and Mary, have been used as possible indicators of her origins (wikipedia.com)