The belief that members of an ethnic group are blood relatives may seem archaic, but it is still very alive today, and it awakens primordial feelings of affiliation. According to this deep-rooted idea of kinship, individuals are only responsible for members of their own ethnic group, and it is only to them that they are obliged to show solidarity. The effects of this belief were seen at two blood drives that the German Red Cross held at a Turkish mosque in the Ruhr region of Germany and that were studied in an ethnographic research project. An analysis shows that the belief in ethnic kinship represents a major barrier to integration and an important factor in perpetuating social inequality among ethnic groups. The Turkish migrants endeavored to initiate an exchange of gifts among quasi-relatives and based their integration strategy on this objective, but their efforts to establish reciprocal exchange relations provoked resistance in the autochthonous population. Herein lies the broader relevance of the primordial belief in blood relations, which constitutes a deep symbolic dimension of social inequality.