OPERROR BTWN ACFT #1 IN DSCNT TO 4000 FT AND ACFT #2 LEVEL AT 4000 FT. RPTR HAD INSTRUCTED ACFT #1 TO TURN TO INTERCEPT THE LOC. CLRNC WAS TAKEN ACKNOWLEDGED BY ACFT #3. RPTR MISSED THE READBACK. ACFT #1 WAS ON A CONVERGING COURSE WITH ACFT #2 WHEN RPTR REALIZED IT HAD NOT TURNED. ACFT #1 WAS TURNED BUT SEPARATION WAS LOST. ACFT #2 WAS TURNED AND MADE AN EVASIVE ACTION DSCNT AFTER RECEIVING A TCASII RA.

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I WAS THE S APCH CTLR RUNNING STAGGERED ILS'S TO RWY 11R AT MSP; ACFT #1 WAS ON FINAL 14 MI OUT WITH TFC 3/4 OF A MI AHEAD ON THE PARALLEL LOC AT 1000 FT BELOW. I ADVISED ACFT #1 THAT I WAS TAKING HIM OFF THE FINAL FOR ADDITIONAL SPACING WITH THE ACFT AHEAD ON THE PARALLEL LOC. I THEN TURNED HIM TO A 170 DEG HDG AND INSTRUCTED HIM TO MAINTAIN 5000 FT. I TALKED TO ANOTHER ACFT AND THEN RETURNED TO ACFT #1 AND INSTRUCTED HIM TO TURN L HDG 080 DEGS AND INTERCEPT THE RWY 11R LOC. I THEN TALKED WITH ANOTHER COUPLE OF ACFT AND COORDINATED WITH THE RWY 11L CTLR TO DSND MY ACFT #1 TO 4000 FT. I THEN INSTRUCTED ACFT #1 TO MAINTAIN 4000 FT. I MADE ANOTHER XMISSION AND THEN REALIZED ACFT #1 WAS STILL SBOUND ON A 170 DEG HDG DSNDING THROUGH 4500 FT CONVERGING WITH A B757; ACFT #2; ON DOWNWIND AT 4000 FT. I TURNED ACFT #2 L TO 250 DEGS; AND THEN TURNED ACFT #1 L IMMEDIATELY TO A 090 DEG HDG AND ISSUED TFC; I THEN TURNED ACFT #2 FURTHER L AND ISSUED A TFC ALERT. HE THEN RESPONDED SAYING HE WAS IN A TCASII DSCNT. CLOSEST POINT OF APCH WAS 1.5 MI AND 500 FT. AFTER REVIEWING THE TAPES; IT TURNS OUT THAT ACFT #3 TOOK THE CALL FOR ACFT #1 WHEN I INSTRUCTED HIM TO TURN L HDG 080 DEGS AND REJOIN THE LOC. ACFT #3 WAS ABOUT 25 MI OUT ABOUT TO JOIN. ALL 3 ACFT WERE FROM THE SAME COMPANY. BETTER ATTN TO READBACKS FROM MYSELF COULD HAVE PREVENTED THIS; HOWEVER ACFT #1 AND ACFT #3 SHOULD HAVE BEEN MORE ATTENTIVE.