We have performed magnetization measurements on Ce(Ru1-xRhx)2Si2 and Ce(Ru1-yMoy)2Si2. The metamagnetic critical fields H(M) of the two systems are well scaled by the average d-electron number. In these solid solutions, the change in the d-electron number overwhelms the volume effect, suggesting a significant role of transition metals in c-f hybridization in CeRu2Si2.