Some chiral twin molecules were prepared and the structure-property relationships in the system consisting of chiral twin molecules and achiral host molecules were investigated. The spacer structure was found to have significant effect on the smectic layer strength and the twisting power in the SmC* phase. C-13 NMR measurements revealed that a chiral twin molecule affects motion of host molecules in the SmA phase. The obtained results are discussed in comparison with our proposed model, where chiral twin molecules are intercalated in the SmC-layers formed by achiral host molecules. The chiral twin molecules may produce a strong correlation in host molecules between adjacent layer but decrease the strength of the smectic layer structure.