sachistu: It looks like this may be father and son <Karpova>. Kalendovsky's book of the Bratislava Congress lists Burian (last name only) in Hlavni A and Burian (also last name only) for Hlavni B.
From Wiener Schachzeitung, we can be fairly sure it was Ludvik playing (and winning) Hlavni B. It would appear Jak (Jakob) Burian played in Hlavni B.
Casopis Ceskoslovenskych Sachistu, Aug-Sep, 1925, p124 indicates Burian (of Moravska Ostrava) played in Hlavni A and Burian (of Brno) played in Hlavni B.
CCS also confirms it was L. Burian who won Hlavni B.
According to CCS, Burian also played in the 'Vedlejsi' (Minor) tournament Group A. In the report on that tournament, Burian is listed as Burian ml. (an abbreviation for 'mladsi' or 'junior') of Moravska Ostrava.
This is why I suspect Jak Burian is Ludvik's son. I can't make myself believe a 3rd 'Burian' showed up from Moravska Ostrava!. However, CCS does not refer to L. Burian as 'st' ('starsi' or 'senior'), which leaves some room for doubt.
Proving the relationship is probably a task for one of the specialists here that do an excellent job of tracking down genealogy.