DFT calculations at BP86/QZ4P have been carried out for different structures of E2H2 (E = C, Si, Ge, Sn, Pb) with the goal to explain the unusual equilibrium geometries of the heavier group 14 homologues where E = Si−Pb. The global energy minima of the latter molecules have a nonplanar doubly bridged structure A followed by the singly bridged planar form B, the vinylidene-type structure C, and the trans-bent isomer D1. The energetically high-lying trans-bent structure D2 possessing an electron sextet at E and the linear form HE⋮EH, which are not minima on the PES, have also been studied. The unusual structures of E2H2 (E = Si−Pb) are explained with the interactions between the EH moieties in the (X2Π) electronic ground state which differ from C2H2, which is bound through interactions between CH in the a4Σ- excited state. Bonding between two (X2Π) fragments of the heavier EH hydrides is favored over the bonding in the a4Σ- excited state because the X2Π → a4Σ- excitation energy of EH (E = Si−Pb) is significantly higher than for CH. The doubly bridged structure A of E2H2 has three bonding orbital contributions:  one σ bond and two E−H donor−acceptor bonds. The singly bridged isomer B also has three bonding orbital contributions:  one π bond, one E−H donor−acceptor bond, and one lone-pair donor−acceptor bond. The trans-bent form D1 has one π bond and two lone-pair donor−acceptor bonds, while D2 has only one σ bond. The strength of the stabilizing orbital contributions has been estimated with an energy decomposition analysis, which also gives the bonding contributions of the quasi-classical electrostatic interactions.