A theoretical analysis for the onset of gas pull-through (entrainment) during discharge from a stratified two-phase region through two vertically aligned side branches has been developed in this paper. Initially, a simplified point-sink model was developed; this was followed by the acquisition of a more accurate finite branch model. The predicted value of the critical height at the onset of gas entrainment was found to be a function of each branches corresponding Froude number (Fr1 and Fr2), as well as the ratio between the vertical distance connecting the centerlines of the two branches and the diameter of the branches (L/d). The predicted values of the critical heights were found to be consistent with the corresponding experimental data at different values of Fr1, Fr2 and L/d. From the basis of the present models, it was established that when increasing the flow through the lower branch, the critical height increased for all values of Fr1 and L/d. In addition, it was found that increasing the vertical distance between the two branches, reduced the effects of the lower branch on the determination of the critical height.