Scott Summers / Cyclops

Main Comics (616)

 * 1)  Jean Grey  - Scott and Jean were strongly attracted to each other since they first met, when she joined the X-Men. They eventually formed a relationship. This was sometimes challenged by the infatuation of Logan for Jean, but it endured.

After the real Jean awakened and was discovered, it was also revealed that Madelyn Pryor was a clone created by the X-Men's enemy Mr. Sinister. Madelyn went insane and died.
 * 1)  The Phoenix - Unbeknownst to Scott and the X-Men, Jean was placed in suspended animation by the Phoenix Force, and replaced by the Phoenix itself, imitating her, and even convincing itself it was her, with no other memories. Naturally,  it carried on the relationship with Scott. This being's power grew to incredible levels, but with it, "Jean's" conciousness was taken over by the insane Phoenix, which killed an entire planetfull of people. Although Professor X subdued the evil personality for a time, when she felt it coming on again, she killed herself rather than allow it to rage again.
 * 2)  Lee Forrester  - After Jean's apparent death, Scott began a relationship with a young woman named Lee Forrester, who later had a relationship with Magneto.
 * 3)  Madelyn Pryor  - Scott then met a woman who bore an incredible resemblance to Jean named Madelyn Pryor. The two fell in love and were married, having a son named Nathan. When Nathan was infected with a virus with no cure in the present, the two had him sent into the future.

Scott and Jean then renewed their relationship and were married.

4.  Emma Frost  - Scott later began to be attracted to their new teammate Emma Frost. A telepath, Emma instigated a psychic affair in which the two shared a vivid mental experience of having sex, the lack of actual physical contact being used as an excuse. Jean eventually discovered the affair, and this obviously put a strain on the marriage. Shortly afterward, Jean was killed in battle. She gave a final psychic push to Scott to allow him to move on. It worked, as Scott later found himself literally kissing Emma over Jean's grave, instigating their new relationship.

Ultimate Comics

 * 1)  Jean Grey  - Some kind of romance must be present between these two in this universe.

Animated Series

 * 1)  Jean Grey  - Jean and Scott are in a relationship in the show.

Films
Logan later participates in events that change the timeline from 1973 (ten years before Jean and Scott joined the X-Men) onward, before awakening in the alternate version of the present that he created, but has no memory of.
 * 1)  Jean Grey  - Jean and Scott are in a relationship in the films. As in the comics, this is challenged by Logan. However, Jean chooses to remain with Scott. She then apparently sacrifices herself at the end of the second film to save the team. However, she turns out to have survived, and evolved into a more powerful, yet insane, form called The Phoenix. The Phoenix's first act is to murder Scott.

In the new timeline, in 1983, we see Jean and Scott first join the X-Men and meet each other, and the buddings of their romance.

When Logan awoke in the new version of the present, he finds both Jean and Scott alive, and in a relationship, noting "It's nice to see some things never change."