Indeed I have more info about your granddad. He was baptized 08-08-1893 in Clanwilliam and married your grandma 27-09-1914 in Leipoldtville.
His parents were: Gideon Johannes David van Zyl (born 19-03-1868) and Maria Berendina Johanna Elizabeth Geysteyn (same family name as your grandma ;-))
I should be glad to receive the data / names of your dad and ma (and yours !!), so I can join them to the database.
If you go to my website www.moustache.nu/genea/parentelen/z-afr-b6/z-afr-b6.frm3.htm you can follow the line back to ''stamouer'' Willem van Zijl & Christina van Loveren.