The Hrnjica brothers are heroes of epic poetry in Bosnia. The names of the brothers are Mujo, Halil and Omer. The epic poetry also mentions their beautiful sister Ajkuna (Bosnian: Lijepa Ajkuna). Mujo is hypocorism of Mustafa. There are several toponyms in the region of Velika Kladuša named after Hrnjica brothers, i.e. Well of Hrnjica (Bosnian: Hrnjičin bunar) or the Tower of Hrnjica (Bosnian: Hrnjičina kula). Songs about the Hrnjica brothers can usually be put in the "Krajišnik" cycle (Bosnian: pjesme o Krajišnicima). (transl. songs about the Frontiersmen) This cycle deals with the frequent raids and battles that happened in Bosnia, which at one time was a border province of the Ottoman Empire.

Mustafa Hrnjica is historical person who was recorded as hajduk in the region of Ottoman held Velika Kladuša in 1641, together with his brothers. The source of this is Vuk Krsto Frankopan Tržački, actually sending a secret list of "Turkish" troop commanders. A part of the document explicitly mentions Mujo Hrnjica:

From Velika Kladuša. This is where we fought the most. Mustafa, the chieftain, the brother of Hrnjica brothers, called Mustafa Kazličić, /Kozličić/

— Vuk Krsto Frankopan Tržački

Halil Hrnjica is most likely a historical person as well, legend has it that he died in a battle at Banja Luka, where his tomb was located.

The Hrnjica brothers descend from village Udbina in Lika. According to legend, their father came from Asia to Udbina and married a daughter of the local nobleman, Hurem-aga Kozlić. All of these legends about the Hrnjica brothers were first made known by Ibrahim Bey Bašagić. The Hrnjica Brothers appear in South Slavic oral epic under several name variants, reflecting regional pronunciation, singer preference, and transcription practices. The most common forms are '''Hrnjica Mujo''' (also Mujo Hrnjica) and '''Hrnjica Halil'''. In some recordings and printed collections, the brothers are referred to collectively as the ''Hrnjići'' or ''Hrnjice''. As is typical of oral epic tradition, family relations, personal epithets, and narrative details may vary between performances.

Within the Bosniak and Krajina epic repertoire, the Hrnjica Brothers appear as recurring heroic figures situated in a frontier setting shaped by ongoing military conflict along the Ottoman–Habsburg border. In epic narratives they are commonly involved in episodes such as raids, rescues, armed encounters, and expeditions undertaken either individually or in cooperation with other frontier leaders. Songs featuring the brothers typically emphasise themes of martial competence, kinship solidarity, and the maintenance of personal and familial honour within a borderland context.

Their representation follows established conventions of South Slavic heroic epic, in which characters are primarily defined through observable actions, public reputation, and participation in conventional narrative situations rather than through sustained psychological characterisation. Narrative structure relies on recurring patterns such as duels, border skirmishes, collective assemblies, and organised expeditions, which recur across different songs and performance contexts within the tradition.