CAPT OF A B757-200 FAILED TO HOLD SHORT OF PARALLEL RWY DURING TAXI AFTER LNDG. TWR HAD ISSUED HOLD SHORT INSTRUCTIONS DURING LNDG ROLL BUT HE DID NOT HEAR. ANOTHER AN ACR ACFT LNDG BEHIND TURNED OFF AND DIDN'T STOP UNTIL PASSED THE HOLD SHORT LINE DUE TO THE PRECEDING ACFT ACKNOWLEDGING A SIMILAR SOUNDING CALL SIGN. TWR ABORTED AN ACFT CLRED FOR TKOF ON PARALLEL RWYS.

Narrative

ON SHORT FINAL LAX TWR TOLD US TO TURN OFF ONTO TXWY P AFTER LNDG ON RWY 25L. AS WE WERE ROLLING OUT; THEY CHANGED THE TURNOFF TXWY TO TXWY N -- 1 TXWY PRIOR. THE FO WAS FLYING THE ACFT AND I TOOK CTL AS WE TURNED OFF ONTO TXWY N. I ACKNOWLEDGED THE TURNOFF FROM TWR BUT DID NOT HEAR TWR TELLING US TO HOLD SHORT OF RWY 25R. I CONTINUED ACROSS RWY 25R ONTO THE TXWY AND TWR HAD TO CANCEL TKOF CLRNC TO AN ACFT ON RWY 25R. AS WE CROSSED RWY 25R TWR CALLED AND SAID HE TOLD US TO HOLD SHORT OF RWY 25R. I DID NOT HEAR CLRNC AND THEREFORE DID NOT ACKNOWLEDGED IT. WE CONTINUED TO THE GATE AS PER GND CTLR INSTRUCTION. SUPPLEMENTAL INFO FROM ACN 421955: LNDG BEHIND COMPANY WITH SIMILAR CALL SIGN. ON ROLLOUT; TWR MADE A XMISSION THAT SOUNDED LIKE IT WAS FOR US BUT USED THE OTHER COMPANY'S CALL SIGN. THEY ACKNOWLEDGED. WE CLRED RWY AND WERE INSTRUCTED TO HOLD SHORT OF RWY 25R. ACFT'S NOSE WAS PAST HOLD SHORT LINE WHEN WE STOPPED. CONFUSION ON RADIO AND MY FAILURE TO REALIZE HOW CLOSE RWY 25L&R WERE -- ONLY 1 HOLD SHORT LINE BTWN RWYS. CALLED TWR. THEY SAID NO PROB.