Under the hybrid excitation of internal flows and external currents excitation, submarine water pipelines exhibit a myriad of intricate dynamic behaviors. Particularly in the context of dual-span pipelines, as compared to single-span configurations, the coupled vibration dynamics arising from flow-induced and vortex-induced phenomena are significantly impacted by the proximity of adjacent spans, resulting in a more complex tapestry of modal vibration characteristics. This study employs torsional and tensile springs to simulate the pipeline-soil coupling. Building upon previous wake oscillator vortex-induced vibration coupling models for dual-span pipelines, this model incorporates the consideration of the effects of internal flow excitation. By utilizing the Generalized Finite Difference Method (GFDM) and the Houblot Method, discretization techniques are simultaneously applied to high-order spatial and temporal terms, culminating in the establish a meshless numerical framework that captures the multi-modal vibrational response attributes of the pipeline. In comparison to preceding numerical outcomes, these results align more closely with experimental findings. The results show that, compared to single-span pipelines, dual-span pipelines exhibit more modal excitations within the same reduced current velocity range; Under the influence of mid-span constraints, the maximum vibration displacement of the dual-span pipeline is concentrated near the supports at both ends; In single-span configurations, there are 1^st-2^nd and 2^nd-3^rd coupled vibration modes dominated by the 2^nd mode, while in dual-span configurations, there are 2^nd-3^rd and 3^rd-4^th coupled vibration modes dominated by the 3^rd mode, demonstrating a phenomenon of coupled mode drift.