The easy way would have been to just buy a Y-splitter, standard available for a few dimes....would have saved you cutting cables etc because this whole thing may very well not work !!
The thing is: you're placing 2 (IR-) Leds parrallel and, unless they're ''equally paired'' (almost never is my guess) the one with the lowest threshold will give light and the other not.
Therefore, my bet is, even if the polarity is correct (which does matter), only one of the 2 will work....
You may try to put them in series though (if that works depends on the electronics ''driving'' the IR led).