Disloyalty aversion: Greater reluctance to bet against close others than the self

•People are more willing to bet on their own failure than a close other’s failure.•However, they are as willing to bet on their own failure as a stranger’s failure.•This occurs for bets that are incentive-compatible and made in private.•Self-signaling that one is loyal underlies this tendency.•This violates economic principles of self-interest and desire to minimize risk.