This paper validates the fertility and union histories of the German Generations and Gender Survey (GGS). One major result from this validation is that the fertility of the older GGS-cohorts is too low, while it is too high for the younger cohorts. For partnership histories, we find a similar bias. In sum, the GGS gives wrong cohort fertility and marriage trends for Germany. We speculate on various sources for this bias in the data. However, we were unable to find a remedy to cure it.