A process for forming a new group of siloxane-based compositions by a one-step co-hydrolysis and the compositions formed thereof. The siloxane-based compositions being functionalized with a carbon-carbon double (C═C) bond and a silicon-hydrogen (Si—H) bond. The C═C bond and hydrogen (H) each being attached directly to a silicon (Si) atom of the silicon-oxygen (Si—O) backbone of the siloxane-based composition. The C═C bond may be from a vinyl or an aromatic radical like a phenyl substituent. The C═C bond substituent provides the functionality needed for forming crosslinkages through standard dehydrocoupling catalysts without the need for siloxane fluids or organic compounds containing alkyl or aryl functional groups. The process provides for varying proportions of silanes as starting monomers to tailor the desired silicon, carbon, hydrogen and oxygen ratios in the siloxane-based compositions or resins. The siloxane-based compositions may be used as precursors or replacement resins in the fabrication of other materials.