We report grazing-angle x-ray scattering investigations of interface morphologies in strained multilayers grown on vicinal Si(111) substrates. Samples with different Ge fractions in the alloy layers show a common feature of wavy interfaces arising from the substrate miscut and step bunching. They differ, however, quite remarkably in the wavy period. Our analyses show that the stress-driven step redistribution should take the responsibility for such behaviours of the interfaces.