Magnetically coupled impedance-source networks can achieve a higher voltage gain with smaller shoot-through duty ratio in comparison with the conventional impedance-source networks without coupled inductors. However, the practical voltage gain is seriously affected by the parasitic resistances in passive components and power devices, which is necessary to be investigated. This article derives and analyzes the effects of parasitic resistances on the voltage gain of magnetically coupled impedance-source networks under three different scenarios: first, different resistance ratio between parasitic resistances and output equivalent resistance, second, different shoot-through duty ratio, and third, different winding ratio. First of all, a generalized equivalent circuit model considering parasitic resistances for the three typical magnetically coupled impedance-source networks - Trans-Z-source, Г-source, and Y-source networks are proposed. Based on it, the effects of parasitic resistances on the voltage gain is mathematically derived and discussed under the aforementioned three different scenarios. And the maximum voltage gain under the consideration of the three resistance ratios simultaneously is also derived. Finally, representative simulation and experimental results are provided to verify the proposed generalized equivalent circuit models, the corresponding mathematical derivations, and the effects of the parasitic resistances on the magnetically coupled impedance-source networks.