Re: Petko/Petyko - Hungarian
Petko as family name can be found in Croatia, Slovakia, Ukraine and Serbia (the area of old Austrian-Hungarian monarchy and old Avars state). People with this family name are different nationality and religion. In Bulgaria Petko is very common first male name.
The similar family names are:
Petkoviæ (Croatia, Serbia)
Petkov (Macedonia, Bulgaria)
I think that Petko as family and first name is very old and not related to any present nations.