In some species, poultry, fish and pigs, full sib families exists. In poultry, hens and cocks can be mated and subsequently they may produce hundreds of full sibs. In pigs an average litter comprises 14 piglets being full sibs. The additive genetic relationship among full sibs is 0.5 and this means that full sib data give indeed information on the breeding value of an individual full sib. In cases where full sibs are born spread over time, older full sibs might be informative for the breeding value of a younger one. In dogs a full sib trained as seeing-eye dog can give information for a full sib to be selected for a seeing-eye dog breeding program. In most species sires are mated to several dams and in this way half sib groups are created. The additive genetic relationship among half sibs is not that high (0.25). Information of a single half sib has a rather low value for an individual half sib to be selected. Only when a high number of half sibs is available, this information is valuable.
In the genomic era, when the individual DNA-composition of a full sib or a half sib group is known and is used for genomic selection, an accuracy of nearly 1 can be realized for the breeding value of individual members. The individual phenotypic information of full- or half sibs can be used to separate genetic and non-genetic effects on the trait of interest more accurately.