Thank you for commenting and I'm glad to hear you are enjoying the stories!
There are a few reasons that Gabe and Marc never had sex. One is that Gabe doesn't want another lover. Another reason, is that Gabe is gone much of the time, which is the primary reason for him and Ryland to invite Marc into their relationship. With Gabe being "out of the picture" so often, it really doesn't make sense for him to start something with Marc. Another reason, which was alluded to in a kind of joking way by Ryland, is that Gabe is in his thirties and doesn't have the same kind of stamina as Ryland and Marc, who are both in their 20s. He is a "one and done" kind of guy and preferred to have sex with his boyfriend over a stranger that he just met. I think the attraction between Marc and Gabe is there, and was very much on display in their first sexual encounter, despite the fact that they never had sex with each other. Maybe later on.
Thank you again for commenting!