A.N. Now I don't officially ship Jason and Marcus together, but I do like the pairing idea enough to do fanwork for it. See I first started thinking about the pairing idea when I re-read the series of strips that had been about Jason having a nightmare about turning into a mini-Paige. One of those strips featured Marcus getting a crush on the female-Jason, even calling him gorgeous. However I knew that this wasn't proof of Jason having hidden feelings for Marcus (especially since the strip didn't reveal Jason's reaction) so I knew that Jason being gay (and Marcus being gay) technically isn't canon. So this story can be whatever you readers want: canon-related or an AU.
It was quite a few years later, and Jason and Marcus were now in high school. Since Jason had gotten over his 'girls have cooties' stage during middle school Eileen and Phoebe were now two of his and Marcus's best friends, though Jason was closer to Eileen and Marcus was closer to Phoebe. Also Eileen had decided that it was time to stop fooling around.
"Hi Jason." She smiled, meeting him at his locker
"Hi Eileen, what's up?" Jason asked.
"Well, now that you've finally matured past your 'girls have cooties' stage I was thinking that it was time to start dating for real." Eileen said. "I...I have always had a crush on you and I know that you've secretly have one on me too."
"Uh...sorry Eileen but...after deciding to befriend girls what I thought was a crush completely went away." Jason admitted.
"What?" Eileen was very surprised.
"Yeah, turns out I was just going through an emotional dilemma of wanting to be your friend and wanting to protect my girl-hating reputation." Jason explained. "As for the Valentines...well, when it came to you either apparently not giving me one or just giving me a store-bought one it only hurt because it felt like you didn't care about me, not because it felt like you didn't really love me."
"Oh...well, how about you give dating me a try anyway?" Eileen suggested. "You know...just in case?"
Jason thought it over.
"Okay, just in case." He gave in.
So he started dating her, but even at the end of the first date the idea of dating Eileen still felt weird. He didn't mind hanging out with her, but acting like a couple didn't feel right to him. Because of this he didn't tell anyone except for Marcus about him and Eileen dating, and asked Eileen not to tell anyone except for Phoebe. Eileen agreed. Marcus seemed to take the news well, but the truth was deep down he couldn't help but feel jealous whenever he saw Jason and Eileen acting like a couple. Phoebe on the other hand was happy for Eileen and Jason and decided that it was time for her and Marcus to become a couple as well.
"Say Marcus, I...well, I've had feelings for you for a long time and I was wondering if you'd like to go out with me." She asked him as he was watching Eileen flirt with Jason.
"Sorry Phoebe, but I'm not comfortable with the idea." He said, wincing at Eileen and Jason.
"What? Oh is this because I'm a friend of yours? Come on Marcus..." Phoebe pleaded.
But Marcus kept refusing, no matter how much Phoebe begged. Eventually Eileen noticed the situation and convinced Phoebe to leave Marcus alone for a while, much to Marcus's relief.