Ethnic Croatian families BRAJENOVIĆ are from DUBROVNIK municipality.
Ethnic Serbian families from Croatia BRAJENOVIĆ lived in DVOR municipality in these villages:
I would have to look at the ship manifest or any other original document before being able to confirm that you ought to be researching that surname at all. Only then you can confirm other things like place of origin or ethnicity of the family, and where to look for vital records.
att: BRAJENOVIĆ ethnic Serbian families in records
Serbian Genealogy Society SGS "Rodoslovlje"http://www.rodoslovlje.com/en