At first, Luke's love was simply a crush like any other. Luke had been aware of his friend Connor's love for a long time and felt bad for even having such thoughts so he never said anything. However, over time when Connor and Bella got together he could no longer help himself and asked Bella out.
He was promptly rejected placing a burden in his heart where he felt that if Connor was never there he would have gotten Bella. With this, he continued to hide his love only showing it sometimes even going so far as to open the games facility with the other two.
They all shared the same vision for the games on paper but the reasoning behind Luke's participation was anything but simple. He wanted to take Bella back no matter how long it took.
Luke thought that his plans were proceeding smoothly until many years ago when Bella announced that she was pregnant. At that time the games were still in their beginning stages so Bella only told Connor and Luke.