MERLIN 3 FLC LANDS ON THE WRONG RWY AT STL.

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I WAS THE CAPT; IN THE R SEAT; AND WAS THE PNF. THE PF WAS UNDER MY SUPERVISION. WE WERE ON APCH TO ST LOUIS; MO; ARPT (STL); RWY 12L. AT THE CTLR'S REQUEST; WE KEPT OUR AIRSPD ABOUT 170 KIAS AS AN ACR ACFT WAS ON OUR R SIDE; INSTRUCTED TO LAND ON RWY 12R. THE CTLR SAID THEY WOULD HAVE TO SEND THAT ACFT AROUND UNLESS WE KEPT OUR AIRSPD UP. I MAINTAINED VISUAL CONTACT WITH THAT AIRPLANE. IT WAS CLOSE BY OUR R SIDE; SLIGHTLY BEHIND OUR R WINGTIP. I WAS NOT COMFORTABLE ABOUT THE SPACING. I TOLD THE CTLR; 'WE WILL STAY ON OUR SIDE IF HE WILL STAY ON HIS SIDE.' HE RESPONDED THAT IT SHOULD BE NO PROB. DUE TO MY CONCERN; AND NOT WANTING TO CAUSE A DELAYED LNDG; I INSTRUCTED THE PF TO MAINTAIN A SPD GREATER THAN 160 KTS OVER THE APCH LIGHTS. I BELIEVED SEPARATION STANDARDS WERE BEING COMPROMISED; AND ASSUMED THE CTLR WANTED US ON THE EXTREME L SIDE. RWY 13 IS PARALLEL TO RWYS 12L/R. AS WE WERE BEING RUSHED; AND CONCERNED WITH SEPARATION; I MISTAKENLY LANDED ON RWY 13; THINKING IT WAS RWY 12L! I DID NOT HAVE TIME TO RECHK THE ARPT DIAGRAM TO DETERMINE THAT THE FAR L RWY IS RWY 13. I SUGGEST 1) THAT RWY 13 NOT BE LIGHTED TO AVOID CONFUSION AT NIGHT; AND 2) THE CTLRS BE INSTRUCTED TO INFORM THE PLT WHEN THEY OBSERVE IMPROPER ALIGNMENT ON FINAL; AND 3) TURBOPROP AIRSPDS USED ON FINAL; NOT JET SPD!