https://www.selleckchem.com/products/gdc6036.html Kinship among interacting individuals is often associated with sociality and also with sex ratio effects. Parasitoids in the bethylid genus Goniozus are sub-social, with single foundress females exhibiting post-ovipositional maternal care via short-term aggressive host and brood defence against conspecific females. Due to local mate competition (LMC) and broods normally being produced by a single foundress, sex ratios are female-biased. Contests between adult females are, however, not normally fatal, and aggression is reduced when competing females are kin, raising the possibility of multi-foundress reproduction on some hosts. Here, we screen for further life-history effects of kinship by varying the numbers and relatedness of foundresses confined together with a host resource and also by varying the size of host. We confined groups of 1-8 Goniozus nephantidis females together with a host for 5+ days. Multi-foundress groups were either all siblings or all nonsiblings. Our chief expectations included that compargest hosts presented and had the highest per capita production of adult offspring. Despite single foundress reproduction being the norm, G. nephantidis females in multi-foundress groups appear to attune sex allocation according to both foundress number and foundress relatedness broods produced by sibling foundresses had sex ratios similar to broods produced by single foundresses (ca. 11% males), whereas the sex ratios of broods produced by nonsibling females were approximately 20% higher and broadly increased with foundress number. We conclude that relatedness and host size may combine to reduce selection against communal reproduction on hosts and that, unlike other studied parasitoids, G. nephantidis sex ratios conform to predictions of both classical and extended LMC theories. © 2020 The Authors. Journal of Evolutionary Biology published by John Wiley & Sons Ltd on behalf of European Society for Evolutionary