Hazrat ‘Ammaar (radhiyallahu ‘anhu) was a man of Qahtaani decent. His father, Yaasir, came to Makkah Mukarramah in search of one of his missing brothers. His two brothers, Haarith and Maalik, also accompanied him on this journey.
Haarith and Maalik returned to Yemen while Yaasir decided to stay in Makkah Mukarramah. He then established an alliance with Abu Huzaifah Makhzoomi. Abu Huzaifah got him married to his slave woman, Sumayya bint Khayyaat, and it was from this union that Hazrat ‘Ammaar (radhiyallahu ‘anhu) was born.
Yaasir and ‘Ammaar lived with Abu Huzaifah until the end of his life. Thereafter, when Allah Ta‘ala made Islam known to the people, then Hazrat Yaasir (radhiyallahu ‘anhu), Hazrat Sumayyah (radhiyallahu ‘anha), Hazrat ‘Ammaar (radhiyallahu ‘anhu) and his brother, Hazrat ‘Abdullah bin Yaasir (radhiyallahu ‘anhu), all embraced Islam.
Hazrat ‘Ammaar (radhiyallahu ‘anhu) had another brother who was older than him. His name was Huraith bin Yaasir, and he was murdered by the Banu Dail clan in the time of jaahiliyyah (pre-Islamic era).
(Extracted from Seeratul Mustafa 1/225-226)