Herein, we disclose an unexpected Si–O–Si cage reorganization that was observed during the standard hydrolytic condensation procedure of tetrasilanol double-decker silsesquioxane (DDSQ) with respective mono- and di-chlorosilanes. The investigation of this process allowed us to propose the possible mechanism of this transformation. The formation of all structures was confirmed by NMR, FT-IR, and X-ray (for eleven examples) techniques and their thermal stability was verified (TGA). Additionally, we revealed unusual intramolecular homocoupling product formation during the silylative coupling reaction of vinyl-DDSQ derivatives. It deserves to be emphasized that these findings are the first example of a thorough investigation of hydrolytic condensation and the silylative coupling procedures in the chemistry of DDSQs.