Stars are dispersed all over the sky within our Galaxy appearing in large varieties of ages and sizes. However, obtaining precise estimates for said traids can sometimes be cumbersome. Fortunately, most stars are found to be part of binary or multiple systems, which allow us to study their orbital motions to derive dynamical masses. In turn, such results can be used to constrain stellar evolutionary models. In this talk I will present my licentiate thesis, which covers how we can detect binary systems, and how we can go about to use fundamental physical laws to derive important quantities such as dynamical masses. I will also present recent results of an orbital fit to a low-mass triplet system which shows a discrepancy between the derived dynamical mass and the theoretical mass obtained from stellar evolutionary models.