In the Dvorsak gazetteer of Hungary, looking for Vecseklo, it says to look in Fulek in Nograd megye. Looking in the FamilySearch catalog for Fulek, Jewish Records is film 642842 which is only viewable at a Family History Library. I searched this film and found the birth records for Zsani, born 18 Apr 1880 in "Wecseklo", Scharolta born 26 May 1881 in Vecseklo, and Gyula born 23 May 1884 in Vecseklo. All have your Geza Haaz and Johanna Kohn as parents. See the attached scans.
In addition there is an Adolf Haasz/Hasz who has children near the same time. One on Sharolta's page and 3 on another page which I also attached. There are a couple more that might be related but I did not download those. Let me know if you want them too.
I searched the marriage records but neither of these couples was there.
However there are a few clues that I will follow up on probably tomorrow.