Kiril Topalov, a member of the Bulgarian Joint Committee on Historical and Educational Issues, has reacted to the positions of their "cousins" from North Macedonia.
Topalov said he is a descendant of Slavo-Macedonians who fled to Bulgaria after the Balkan Wars.
"About two million of us are descendants of former Slavo-Macedonian immigrants. This determines the extent of the categorisation with which we deal with in the Macedonian issue," the academic said on a show on Bulgarian National Television (BNT).
"I cannot accept that my grandfather, who died for Bulgaria, was not Bulgarian. In North Macedonia they are trying to change the identity of our grandparents from 100 years ago, and they are shouting that we have changed their identity," he continued.
"We accept and allow things that no one else would do. How did the national identity change in 60 years?" he questioned.
According to the Skopje-based Express website, the Bulgarian professor referred to the Prespa Agreement with Greece.
"The issue with the Greeks was resolved so that they do not face problems at all.
"They held two rallies of 1.5 million (protesters) each, thus showing the world, and their neighbours what awaits them and what is the position of the Greek people and all Greek governments, left or right.
"I have talked to Greek politicians about this. And so in Skopje they accepted the name North Macedonia. The Greeks let them think, to decide.
"Finally, our cousins hit their foreheads on the doorstep of the Greeks and said 'we accept everything, we leave antiquity.'
"In a few months, they have managed to reprint their books and get rid of everything related to antiquity and all their lies.
"We have been talking to them for 3.5 years and they have not changed a single letter in their books in which they write that we are Tatars, Turks, Mongols, fascists.
"They have already stolen our history. Their society has already turned against Bulgaria," Topalov concluded.