Structurally tuned multiferroic state is demonstrated for BiFeO3-based compounds. The electric and magnetic orders are strongly affected by the coexistence of R3c and Cm phases, i.e., by structural softness through monoclinicity, which leads the multiferroism to be driven by the same cation. The Cm phase enhances the ferroelectric and magnetic responses through Bi/Ba–O and Fe/Ti–O bonds by influencing structural distortions and ion valence. We also show the strong correlations between ferroic orders, structural arrangements, and tuning of the ion valence in the perovskite B site.