In the Zoldyck family is something known about the grandmother and the grandgrandfather?
Zeno Zoldyck is the father of the Silva Zoldyck. It is clearly stated in this family chart which in the HxH wiki. In the family tree, Maha Zoldyck is the grandfather of Zeno, also he is the oldest living person in Zoldyck Family. 



There are no mentions about Zenos' wife (mother of Silva). Below image shows the family of Zoldyck but Zenos' wifes' image is missing there also. Also, Kikyo is the only women that have mention and appeared in the HxH from Zoldyck family (apart from Silvas children). I think that mainly because of they joining Zoldyck family from the other families.