The aim of this research was twofold: (1) to find out if there is a relationship between the rate of social discounting, and the degree of consanguinity with the sharing group members, (2) to find out if the rate of social discounting correlates with two personality traits: Rotter's locus of control, and agreeableness from the Costa's and McCrae's Five Factors personality model. Participants completed a social discounting questionnaire, Rotter's I-E Scale, and Costa's and McCrae's NEO FFI questionnaire. In the social discounting questionnaire participants' task was to indicate their preferences regarding pairs of hypothetical amounts of money: one to be received for themselves, and the other one to be shared with the group of relatives or strangers. The rate of social discounting was higher when the sharing group consisted of strangers as opposed to the group consisted of relatives. In addition, a positive correlation was revealed between the rate of social discounting and the degree of agreeableness. The results support a hypothesis stating that people prefer to share a reward with relatives rather then with strangers. The finding can be explained within an evolutionary psychology framework. It can be understood as an example of kin altruism.