The Annalista Saxo names Sigefridus, '''avunculus''' Esici comitis de Ballenstide, filius Odonis incliti marchionis, "avunculus Esici comitis de Ballenstide", translates today into nephew, but in this case, it would stand for sororal nephew, according to how the family is descripted, Esiko, count of Ballenstedt would be a son of Sigefried's sister, as it's the only natural interpretation.
Hidda von Ballenstedt it's also supported by indirect evidence, as Esiko named his son after Hidda's husband, thus his father, Adalbert.
Even if only mentioned in one source, cited above, Esiko should be placed as Hidda's son, unfortunately, this profile of Esiko is locked by a notorius hostile to logic curator, it needs to be unlocked.
Correction in order to make you all understand, "avunculus" means "uncle", it stands both for either the fathers brother, or the mothers brother to a child, in this case, Sigefried is the brother of the mother to Esiko, thus Esiko is his sororal nephew, = sisters son and Sigfried is an uncle to him on his mothers side.
Uncle = the brother of one's father or mother or the husband of one's aunt.
Esiko, count of Ballenstedt is now created in his right place of the tree, as the son of Graf Adalbert von Ballenstedt och Hidda von Ostmark, according to MedLands, it is his father who lacks parents, "ADALBERT [von Ballenstedt], son of ---. "
http://fmg.ac/Projects/MedLands/MEISSEN.htm#dauHodoMAdelbert
Esiko war ein Sohn eines namentlich nicht bekannten Vaters (Adalbert), der Vogt der Klöster Nienburg und Hagenrode war, und einer namentlich nicht bekannten Tochter (Hidda) des Markgrafen Hodo I. der Ostmark. Ob Uta, Ehefrau von Markgraf Ekkehard II.
Esiko war mit einer Mathilde, wahrscheinlich Mathilde von Schwaben, Tochter von Herzog Hermann II. von Schwaben (oder mit Mathilde von Werl?) verheiratet.
Kinder waren
Otto
Adalbert II., Graf von Ballenstedt
Adelheid ∞ Thiemo, Edler von Schraplau (nähere Angaben zu beiden nicht bekannt)
https://de.wikipedia.org/wiki/Esico_von_Ballenstedt
Finished, this is the correct profile according to the sources, parents deduced from that Siegfried's sister married the father of Esico.
Esiko, count of Ballenstedt
This is the locked profile without any derived information.
Esiko, count of Ballenstedt
Think that they need to be merged, but we need a good curator to do that, someone that understands that you actually can obtain something indirectly from a specified source in order to establish what's missing in another case, in this case, the not directly mentioning of Esiko's parents.