Values in brackets are 95% credible intervals. ‘Sex’ indicates difference in males relative to females; ‘Age’ is the effect in years; ’IR’ is an individual’s internal relatedness value; ‘Season’ is the effect of breeding season relative to non-breeding; and Age*IR is the interaction. Random effect variance estimates, genetic heritability (h2) and proportion of variance attributed to maternal effects (ICCME) are all presented on both latent and observed data-scale. Parameters estimates were converted to the observed data-scale using QGglmm package. N=195 individuals, for whom maternity was known, born to 106 mothers.