This is a total crack story so please do not expect anything else. Takes place during season 3 episode 7 at Primatec, spoilers for the revelations of the beginning of the season as well as for Caitlin in season 2.
Peter walked in, straight over to the man waiting on the couch. "Peter, you stayed," Gabriel observed as he rose.
"I wasn't going to leave you," Peter explained, looking around the room for any threats.
"Why after what I did, what I did to you, why do you care?"
"You changed. I changed. Nothing is the same anymore," Peter explained. "We need to leave."
"Peter?" Gabriel began apprehensively, continuing only once his brother met his eyes. "What happened to you after Kirby Plaza?"
Peter smiled sadly; remember the past when so much was different, so much was wrong between them, "It's a long story. I ended up in Ireland at one point, met this great girl, Caitlin, who…" Peter suddenly stopped talking. A look of complete and utter panic filled his face.
"What is it?" Gabriel asked, cautiously approaching his new found brother.
"Oh, shit!" Peter exclaimed as he remembered his one time love interest, written out of the show way too quickly. "I left her in the future."
"You what?"
"We were young and confused and….How could I have just forgotten about her?" Peter asked in desperation, as tears began to stream down his face.
"These things happen," Gabriel explained, laying a comforting hand on Peter's shoulder in what was, to him, and unfamiliar gesture.
"These things happen?" Peter spat out. "To who?" Peter pushed off the wall to meet his brother's gaze. "I left my girlfriend to die in a terrible future that is now gone and destroyed."
"Maybe she returned on her own or maybe she is just stuck in this version of the future," Gabriel speculated, "You don't know?"
"Yeah, I guess. And now that my father…our father stole my powers I will never know." Peter silently cried for several minutes before facing his brother again. "Hey, maybe she's making waffles with you and Noah."
Gabriel looked dumbfounded, "What?"
"It was this future I was in and…When you gave me your powers."
Gabriel explained with a shrug, "Well, I do like waffles."