Yes, there is cheating. I wasn't put off by it in this story because the two dating characters really never clicked with each other. Javier is really into Gabe, but Gabe isn't feeling it. Gabe should not have even dated Javier in the first place, but he kept thinking he would start to feel something if he just keeps trying. Gabe cheats with Javier's cousin. It's actually funny because Gabe doesn't think Mateo likes him as a person, let alone wants to get intimate. This is Gabe and Mateo's story.
It's hard not to have a spoiler when reviewing a short story.