Your wife's relative is most probably right - this yataghan is deffinitely Balkan, and it could be from Serbia, or Monte-Negro, or Bosnia, or Macedonia, or even Bulgaria. The silver inlay on the bolster and the hilt strap. Are there any inscriptions or markings on the blade? I am confused as to what do you mean by "the black in the lower guard". When you write lower guard, do you imagine the sword with the yip up or down? Actually, yataghans as distingusihed by the lack of guard and most probably you are referring to the pommel (the ears).
This is a very nice sword, especially if it is your first and only one.
Congratulations.