Information from the Byzantine historian Scylitzes on rebellions in Bulgaria under Tsar Peter, and on Tsar Samuil's Bulgarian origin
late 11th - early 12th c.

The Tsar of the Bulgarians, Peter, was opposed by his brother Ivan together with other Bulgarian noblemen. But Ivan was caught, whipped and thrown into jail and all the others were subjected to the heaviest punish¬ments. ..
Mihail, the other brother of Peter, also dreamed of seizing power in Bulgaria. He captured a strong fortress and spread unrest throughout the Bulgarian state and many Bulgarians joined him. He soon died, however, and his adherents, because they were afraid of Peter's wrath, entered the Byzantine lands by way of Macedonia, Strymon and Hellas ...
Peter, Tsar of the Bulgarians, renewed the peace immediately after his wife's death and concluded a treaty with the Emperors and gave as hostages his own sons Boris and Roman. Not long afterwards, he died. After this his sons were sent to Bulgaria to occupy their father's Kingdom and to stop the advance of the Kometopouli. Because David, Moses, Aaron and Samuil, sons of one of the powerful comites of Bulgaria, were / planning an uprising and were/ spreading unrest throughout the Bulgarian State ...

Source:
Georgii Cedreni Compendium historiarum, ed. Bonn II, pp.312, 313, 346, cf; ГИБИ, VI, p.257; the original is in Greek

The Byzantine historian Scylitzes describes how Samuil, son of a Bulgarian noble, became ruler of all Bulgaria
llth-12th c.

Immediately after the death of Emperor Ioannes the Bulgarians rose in revolt and four brothers were chosen to govern them: David, Moses, Aaron and Samuil, sons of one of the all-powerful comites of the Bulgarians and for this reason named Kometopouli... Of the four brothers, David was immediately tiled by some Wallachian vagabonds between Castoria, Prespa and the so-called 'Fair Oak Wood.' While besieging Seres, Moses was hit by a stone cast from the wall and died. Aaron was killed by his brother Samuil on July 14 in a place called Razmetanitsa, together with all his kin, because he was a supporter, so they say, of the Byzantines, or because he was trying to seize power himself. Only his son Vladislav Ivan was saved by Samuil's son Radomir Roman. Thus Samuil became the absolute ruler of all Bulgaria ...

Source:
Georgii Cedreni compendium, op. cit, pp. 434-435; cf. ГИБИ, VI, p. 275; the original is in Greek