The kinematics of young stellar clusters reveal key insights into the dynamic state of their parent molecular clouds. More than fifty years ago, Lynden-Bell showed that violent relaxation during collapse leads to a velocity dispersion independent of particle mass. However, in collisional relaxation, energy equipartition is expected, where massive stars have lower velocity dispersions than low-mass stars. Recent studies of clusters like Orion and the Lagoon Nebula, as well as numerical simulations, show that stars in collapsing clouds tend to have constant velocity dispersion. In contrast, turbulence-supported clouds exhibit the opposite trend: massive stars have larger velocity dispersions. For a better understanding of these mechanisms, I analyzed turbulent-supported clouds in numerical simulations. In this talk, I will show results from a process we refer to as “accretion-driven gravitational tightening,” where massive stars form in denser regions, accrete more efficiently, and interact strongly with nearby stars, increasing their velocity dispersion, while low-mass stars, being more isolated, experience a weaker effect.