Abstract: We study the joint relative localization and formation control problem of multi-agent systems in a GPS-denied environment from the perspective of biological altruism. First, inspired by biological altruism behavior, we design an altruistic decision-making mechanism to determine when agents should perform altruistic behaviors to enhance inter-agent observability. Then, we develop a parameter-estimation-based online adaptive relative position estimator, which relaxes the persistent excitation conditions imposed by classical approaches such as least-squares estimators. Based on Hamilton rule, we prove that altruistic behaviors contribute to the joint localization and control, and we demonstrate the proposed scheme through multi-agent formation control. Finally, numerical simulations are provided to validate the effectiveness of the proposed methods.