Yes, you can combine two antennas aimed in the same direction for more gain, but they must be identical antennas, and the two feed lines must be the same length. This is what Calaveras has done with his two 91XGs:
http://www.aa6g.org/DTV/index.html
The theory predicts a gain of 3 dB, but the most you can expect when using a splitter in reverse as a combiner is 2.5 dB because of the internal loss of the combiner.
The reason why you must have identical antennas, aimed in the same direction, with identical length feed lines is because you want the two signals to arrive in phase at the combiner.
Under any other conditions, it might or might not work; trial and error, good luck, you are on your own.
First, each antenna alone must get what it should. If you then combine them and some channels are missing, then it isn't working.
If you are combining two antennas that have printed circuit baluns, they will be in phase. If you are combining two antennas that have the older style 300 0hm to 75 ohm pigtail baluns, you must reverse the 300 ohm wire leads on ONE of the baluns to see which way gives the most gain. When they are not correctly phased together, the main lobe splits in two with a null between them at the aiming point.
Sometimes you want the two antennas out of phase, to split the main lobe in two. This is done when you want strong local signals placed in the null to make them weaker, so that one of the two lobes can pick up weaker signals from another direction. This is called the two-antenna-trick (outdoor version), and could be used in your case to make KCTV weaker. See Example 3:
http://www.hdtvprimer.com/antennas/ganging.html
I assume you are talking about two UHF or two VHF antennas. If you are combining a VHF antenna with a UHF antenna, they should be combined with a UVSJ UHF/VHF combiner, not a splitter in reverse.