Interaction between twin jets is a vital phenomenon in jets mixing and noise control, and comprehending the interaction between jets helps develop many applications such as aircraft exhaust, burners and injectors. Numerical simulation results of parallel twin jets emerging from convergent nozzles at four (3, 4, 5 and 6) nozzle pressure ratios are presented in this paper. The underexpanded sonic twin jets are simulated using the Reynolds-Averaged Navier-Stokes equations based two-equation turbulence model, namely SST \(k-\omega \) . Centerline Mach number decay, supersonic core length and shock cell length properties are presented to investigate the effect of nozzle pressure ratio on twin jets interaction.The results demonstrate a linear increase in the supersonic jet core length and the length of the first shock cell, with an increase in NPR, which is attributed to the jet expansion. The appearance of the Mach disk is observed for highly underexpanded twin jets, whereas it is absent at NPR 3. The present simulated twin jet results at various NPRs are consistent with experimental results, and they are qualitatively similar.