The present work analyzes the effect of alloying supported Pt clusters with Ge in different stoichiometric ratios, to probe the degree to which Ge concentration can improve the sintering and coking resistance of the catalyst. The computed phase diagram suggests the feasibility of forming varying stoichiometries, although the prevalent phases correspond to the 1:4, and 1:4 Ge to Pt ratio. We note that in the presence of oxygen, the excess Ge could separate from the Pt and form an oxide -the effect not addressed in this work. The adsorption and mechanistic studies reveal that the clusters featuring the 1:4 Ge to Pt ratio feature the highest stability and resistance to deactivation by means of sintering and coking, while retaining the catalytic activity toward ethane dehydrogenation. Increasing the Ge content leads to reduced catalytic activity, and at 1:1 Ge:Pt ratio the clusters stop binding and activating ethane. On the other hand, pure Pt clusters dehydrogenate ethane and ethylene barrierlessly, and thus easily coke. Therefore, we conclude that the Ge content affects cluster stability, dehydrogenation activity, and selectivity. The analysis of the electronic structure suggests that Ge forms strong polar covalent bonds to Pt, and quenches the unpaired spins on Pt. This is the key factor impacting the reduction of activity toward ethylene dehydrogenation. The singlet-triplet energy gap increases with the Ge content. Ge also transfers electrons to Pt, and in Pt 4 Ge, the charge transfer is the most adequate for achieving the balance between activity toward ethane dehydrogenation and selectivity against ethylene dehydrogenation. Finally, we note that this study uses a model support (MgO) and only one Pt cluster size, due to the complexity of the configurational space.