Though Alex himself was also cheating with Gideon at the time of his on and off relationship with Cain, and even had a child with Gideon, Alex still regarded Cain's betrayal as more damaging than what he did.
After all, Alex only started seeing Gideon after he found out that Cain was cheating on him with his own best friend.
He had tried to forgive them, he even gave his love to dear Zach. But Alex knew that no matter how much he wanted to forget what happened more than twenty years ago, one day the shadow of his past would catch up with him and make him realize that running away from everything was never the answer.
One of his hands that hugged his knees slowly loosened, and right after he wiped his tears that had him choking in his own sobs, Alex slowly moved his palm to grasp his neck, tracing the remnants of Gideon's mark on his body.