Kotechind von Sachsen - Sources for more siblings than Medlands has

Medlands finds proof for only one son: Ekkehard von Sachsen (-killed in battle 25 Sep 936) http://fmg.ac/Projects/MedLands/SAXONY.htm#OttoErlauchtedied912A

LIUDOLF (-before 30 Nov 912). m ---. The name of Liudolf's wife is not known. Liudolf & his wife had one child:
a) EKKEHARD (-killed in battle 25 Sep 936). Widukind names "Ekkardus filius Liudulfi", when recording his death[180]. m ---. The name of Ekkehard's wife is not known. Ekkehard & his wife had [one possible child]:

What are the sources for Wendelgarde von Sachsen and Ekkehard von Sachsen as other siblings?