The existence, thermodynamic stability, and gas phase acidity of two series of dinuclear Lewis-Bronsted superacids (HB2F7, HAl2F7, HAlBF7 and HAs2F11, HSb2F11, HAsSbF11) were investigated on the basis of ab initio MP2 and CCSD(T) calculations. All the systems studied are characterized by large acid strengths manifested by the Gibbs free deprotonation energies significantly lower than that of the sulfuric acid. These results are related to the high electronic stabilities of their corresponding superhalogen anions (natural precursors of superacids). Furthermore, our investigations show that the superacid molecules containing two different central atoms are stronger in the gas phase than their classical counterparts.