MULTIPLE RWY OP PARALLEL ILS APCHS. ACR X HAD LTSS FROM ACR Y TCASII RA EVASIVE ACTION TAKEN. SYS ERROR.

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I WAS WORKING RWY 3L FINAL APCH COURSE; I LET THE OTHER CTLR KNOW I WAS NEXT FOR THE APCH DURING STAGGERED TURN- ONS; AND ADVISED WHAT ALT I HAD ACR X DSNDING TO 3000 FT. THE OTHER CTLR WAS TO FOLLOW AND TURNED ACR Y TOO EARLY TO JOIN THE PARALLEL APCH COURSE. THE SUPVR IN CHARGE CAME OVER AND SAID IT ISN'T GOING TO WORK. HE DIRECTED ME TO STOP DSCNT ON MY ACR X. I COMPLIED WITH HIS VERBAL COMMAND AND TOLD ACR X TO STOP DSCNT AND TURN L HDG 300. ACR X ACKNOWLEDGED AND EXECUTED. I REITERATED THE TURN AND THE CREW ACKNOWLEDGED AGAIN THAT THEY WERE IN THE TURN. CONFLICT ALERT ACTIVATED. SUPPLEMENTAL INFO FROM ACN 257723: I WAS VECTORING TOWARDS THE RWY 3R FINAL STAYING EITHER 3 MI OR 1000 FT FROM ACFT ON VECTORS TO RWY 3L. I OBSERVED THE ACFT ON FINAL RWY 3L STILL AT 5000 FT AND I WAS AT 4000 FT HDG 270. I TURNED TOWARD THE FINAL AND DSNDED EXPECTING TO REMAIN AT LEAST 1000 FT BELOW. MY ACR Y DIDN'T DSND AND THE OTHER ACR X DID AND WE LOST VERT SEPARATION. I HAD PREVIOUSLY PROMPTED MY ACR Y TO EXPECT A TIGHT TURN TO FINAL; SO APPARENTLY HE TURNED AS REQUESTED WITHOUT STARTING A DSCNT. SUPPLEMENTAL INFO FROM ACN 257726: ACR Y ON A BASE LEG ON APCH TO RWY 3R AT DTW. THERE WERE APCHS ALSO TO RWY 3L BEING MADE. THERE WAS SOME CONFUSION WITH ACFT THAT WERE AHEAD OF US. DURING THIS TIME WE WERE ON A 330 DEG HDG AND WERE GIVEN A LATE TURN ON TO FINAL. CTLR GAVE US AN IMMEDIATE TURN TO 090 DEGS WHEN TCASII WENT OFF. WE GOT AN RA TO DSND AT 500 FPM. FO (FLYING) PUSHED ACFT OVER 1000 FPM; AND WE GOT A NEW RA TO CLB. WE WERE IMC; SO I DO NOT KNOW HOW CLOSE THE CONFLICT WAS. THE WHOLE SIT APPEARED TO ME THAT THE CTLR WAS TIRED; COULD HAVE BEEN THE END OF HIS SHIFT; AND THAT HE WAS TRYING TO EXPEDITE TOO MANY AIRPLANES.