Local structural rearrangements in lead-based complex perovskites of the type (Ba1-xPbx)(In0.50Nb0.50) O-3 responsible for transition from ferroelectric [Ba(In0.50Nb0.50) O-3] to relaxor [Pb (In0.50Nb0.50) O-3] are examined by careful analysis of their Raman spectra. Subtle changes in the bonding brought about by the differences in the chemical nature of A-and B-site cations have been correlated with the dynamic A-O-B coupling. Deviations in the local structure as a result of such bonding preferences have been confirmed by studying the changes in the Raman spectra when Nb5+ is substituted by Sn4+ as the third B-site cation.