[Blood group expertises including related presumptive fathers (author's transl)]

In four affiliation cases with two or three brothers involved as putative fathers, exclusions of non-fathers were obtained by the application of the so-called isoelectrofocusing systems (twice by PiM subtypes, once by PGM1, TfC and Gc1 subtypes) as well as by GPT and the extended Gm system. In three cases a discrimination between the involved brothers was possible, in a fourth case both brothers were excluded from paternity. Special problems of anthropological expertises and of biostatistics in cases with closely related putative fathers are discussed. Possibilities to refute false statements of the alleged men, claiming sexual intercourse of the mother with their own relatives in order to invalidate positive biostatistical evidence, are pointed out.