The Regional Security Complex Theory (RSCT) developed by Buzan and Wæver (2003) has conventionally treated the Indian Ocean Region (IOR) and West Asia as analytically distinct security complexes, connected only loosely through great-power overlay. The 2024 enlargement of BRICS which brought Egypt, Ethiopia, Iran, and the United Arab Emirates into full membership alongside founding member India, with Saudi Arabia occupying an unresolved associate status has drawn actors from both complexes into a single multilateral institutional framework. This paper asks whether this development constitutes a genuine merger of the two regional security complexes, an instance of institutional overlay, or a distinct pathway of regional change that RSCT has not yet theorized. Using a qualitative, historical-comparative method that examines BRICS summit declarations, energy and connectivity linkages, and the persistence of intra-bloc security frictions, the paper argues that BRICS enlargement has produced institutional convergence without corresponding security convergence. This decoupling carries direct implications for India, which now occupies the institutional seam between both complexes and must manage this convergence while preserving its strategic autonomy.