A Boeing 737 (B737) aircraft was being radar vectored onto final approach to runway 16R at Sydney from a right base, whilst another B737 aircraft was already established on a straight-in approach from 4,000 ft to runway 16L. The aircraft being radar vectored was given an initial instruction to turn right onto 060 degrees and descend to 3,000 ft, followed by a further instruction to turn right onto 130 degrees to intercept the 16R localiser. However, this instruction was given late, resulting in the aircraft passing through the runway 16R extended centerline at 3,500 ft, conflicting with the leading B737, already established on final to runway 16L. The crew of the following aircraft had the other aircraft in sight at all times. At their closest point, separation was reduced to 1.2 NM laterally and 700 ft vertically. Instructions were then issued to both aircraft to resolve the confliction.