Fax and Mang are the terms used to refer to the pairing of Max and Fang throughout the series. Dax and Mylan are the terms used to refer to the pairing of Max and Dylan when Dylan appears.
Max and Dylan (Mylan)
Dylan is the clone of a Dylan who died in a car accident. He is supposedly to be Max's "perfect other half," but Max thinks her true soul mate is Fang, until Fang leaves Max and the rest of the Flock in the end of FANG. In ANGEL, while Max is crying in a tree, Dylan and she fight in midair -- then, when she least expected it, Dylan kisses Max and she starts to think that Dylan maybe is her other half. In the next couple chapters, Jeb and Dr. Gunther Hagen tell Max that to ensure the survival of the earth, Max and Dylan
should must produce heirs after Max dies, or how they stated it, "Go off to Germany and have kids together."
Later, while the Flock is in Paris with Fang's Gang to stop the Doomsday Group, they kiss on the Arc de Triomphe while it's drizzling and Max says:
And for a long time, it was just the two of us, silhouetted against the Paris skyline, the night deepening around us.
And it felt… right.
And kind of beautiful.
[Nevermore Mylan coming soon.]
Max and Fang (Fax)
Max kisses Fang for the first time in the Angel Expireiment after Fang got beaten up in a fight with Ari down at the beach. In School's Out -- Forever, Fang is saw kissing the Red-Haired Wonder, making Max incredibly jealous. Her date out with Sam later in the book was probably a comeback. In the third and fourth books, Fang kisses Max but it always ends up Max fleeing from him to escape the "sheer terror," but in the Final Warning, Max had said, "It was incredible. I loved it. I loved him." But when the Flock was later introduced to the scientists of the Wendy K, Max started to envy again as Fang gotten cushy around Brigid Dwyer. In MAX, there was a kiss when Fang said he chooses her, and that time, Max didn't run away screaming. Another time, Fang turned down a meal with Brigid so he could go on a date with Max. They also shared a kiss near the end of the book when Max was going into the deep waters to search for Angel and her mother [Nudge had commented ZOMG]. At the end of MAX, Fang and Max shared a kiss in midair, and Angel had given them a thumbs-up. In FANG, they shared many kisses and, in the end, were kicked out of the Flock due to an Eraser attack while they were supposed to shop some groceries. At the end of FANG, Fang leaves Max saying it was for the greater good and that he will meet Max again in 20 years at Lake Mead if the world is not destroyed.
[Nevermore Fax coming soon.]
The majority of Maximum Ride readers support this couple as opposed to Dylan and Max.