Does anyone have other sources as proof of Eberhard being the son of Meginhard and Evesa and brother of Meginhard Graaf van Hamaland?
Medlands has this: "After Godefrid was killed in 885, the emperor appointed the Saxon Graf Eberhard as duke and, after Eberhard was murdered in 898, his brother Meginhard was appointed. No later mention of this imperially created Frisian duchy has been found in the primary sources so far consulted and it is assumed that it lapsed as separate counties developed in Frisia. Meginhard is probably identified with the early 9th century Graaf van Hamaland of the same name."http://fmg.ac/Projects/MedLands/HOLLAND.htm
but then forgets about him here: http://fmg.ac/Projects/MedLands/HOLLAND.htm#WichmannHamalanddiedaft...
Would be great to find additional corroboration.
A quick search gave me this (don't know the quality of the site): https://www.graafschap-middeleeuwen.nl/joomla/index.php/adel/graafs...
You could try to translate it with Google translate or https://www.deepl.com/translator
There are links in the https://www.graafschap-middeleeuwen.nl/joomla/index.php/adel/graafs... document to Rerum Germanicum