This data set represents a reanalysis of human blood plasma samples measured by SWATH-MS of 36 pairs of monozygotic and 22 pairs of dizygotic twins that were sampled at two longitudinal time points (Liu et al., 2015, PMID:25652787). The data were used to determine the overall quantitative variability of 4322 peptidoforms in the sample cohort and to assign the measured variability to heritability, environmental or longitudinal effects.