Although fully understanding of the conflict between relatives is a longstanding quest for evolutionary biology, most parts of selective forces favoring aggressive competition among siblings have not been unraveled. Here, we examined evolutionary factors driving sibling aggression by phylogenetic comparative analyses on 33 Tanganyika cichlid species with different parental care patterns and foraging modes. We tested three non-conflict hypotheses related to the evolution of sibling competition under parental care, cooperative breeding hypothesis, foraging pattern hypothesis and narrow nest hypothesis. Phylogenetic generalized least squares (PGLS) show that intense sibling aggression may have evolved in cooperative breeding species and benthos and algae feeders of substrate-brooding species (not in mouth-brooders), which support the first two hypotheses. However, inconsistent with the third hypothesis, the density of fry did not affect sibling aggression. Additionally, we show that intense sibling aggression may have evolved smaller clutch size (number of eggs in ovary) in substrate brooders. We can conclude that the evolution of sibling competition in Tanganyika cichlids should be strongly related to their social system and foraging modes, which may consequently affect the clutch size adjusted by their mothers.