High-resolution synchrotron X-ray and neutron powder diffraction data demonstrate that, in contrast to recent reports, SrFeIrO adopts an I1̅ symmetry double perovskite structure with an abc tilting distortion. This distorted structure does not tolerate cation substitution, with low levels of A-site (Ca, Ba, La) or Fe-site (Ga) substitution leading to separation into two phases: a stoichiometric I1̅ phase and a cation-substituted, P2/ n symmetry, aac distorted double perovskite phase. Magnetization, neutron diffraction, and Fe Mössbauer data show that, in common with SrFeIrO, the cation substituted SrA FeGa IrO phases undergo transitions to type-II antiferromagnetically ordered states at T ∼ 120 K. However, in contrast to stoichiometric SrFeIrO, cation substituted samples exhibit a further magnetic transition at T ∼ 220 K, which corresponds to the ordering of J ≠ 0 Ir centers in the cation-substituted, P2/ n symmetry, double perovskite phases.