"It's all about the mixing of families through male friendships. A Yazidi man chooses another man to become his blood brother – the man can be from among the Yazidi or they can be from another religion, such as Islam - and the ritual occurs when the would-be blood brother holds the son of his friend during a male circumcision ceremony. The blood from the circumcised child falls onto the clothing of the blood brother and it symbolises the tie between the two men and their families."