The Cyclops/Wolverine/Jean Grey love triangle is one of the most infamous (and annoying) parts of X-Men canon. Despite each of them getting involved in various other relationships and marriages over several decades, this love triangle frequently creates drama, especially during big events. In the Dawn of X relaunch, however, the three have seemingly finally transcended the love triangle and entered the next logical stage: A polyamorous relationship.
Many fans were excited to see this shift, but others expressed confusion at the concept of longtime rivals Cyclops and Wolverine 'sharing' Jean, or of all three being in an equally romantic and sexual relationship. Some have pointed out that the relationship may be the result of Xavier's telepathic influence. While this could be true, it's more likely that after decades of hiding their feelings -- from themselves and each other -- Logan, Scott, and Jean have finally come together in a healthy polycule.
There's no denying Wolverine and Cyclops have fought over Jean, or that Cyclops was hurt by her feelings for Logan. However, by the '90s, the three more or less managed to come to terms with the situation. Cyclops was able to discuss it with his wife Jean and even tease her; both were on friendly terms with Wolverine, who rooted for their relationship even when it became strained. This kind of equilibrium in a love triangle is rare even today and could easily translate into a full-fledged poly relationship.
A popular misconception even among comic readers is that Cyclops and Wolverine hate -- or at least greatly dislike -- each other. While this was certainly true for a time when Wolverine first joined the X-Men, for most of his time with the team he's been fine following Cyclops' lead and he trusts Scott's tactical and strategic abilities.
In turn, Cyclops generally considers Wolverine to be one of his most capable and dependable deputies and literally trusts him with his life and the lives of others. Off-duty, the two are also on fairly friendly terms and their initial antagonism has evolved into (mostly) good-natured ribbing and snarky comments.
This was probably most apparent during the post-M Day, pre-Schism period, when the looming extinction of mutants required the X-Men to drastically change their ways and do whatever it took to defend themselves and their people. One of these changes was a secret kill squad, sanctioned by Cyclops and led by Wolverine, operating under the X-Force name. The shared burden of this secret and the terrible things it did for the greater good probably tied the two X-Men closer together than ever before, though it also caused conflicts that eventually climaxed into the ideological split of Schism and the temporary end of their friendship.
For some readers, one of the hardest parts of a Wolverine/Cyclops/Jean polycule is the possibility that Wolverine and Cyclops might be in a relationship with each other as well as Jean. While it has never been explicitly stated in X-Men canon that Logan and Scott are romantically or sexually interested in each other, both characters have been queer-coded throughout their history.
Scott's acceptance and understanding of Jean's attraction to Wolverine sometimes goes above and beyond just being a good partner and borders on being attracted to the other man as well. Even when he's being jealous, Cyclops' grumbling about how cool and dangerous and attractive Wolverine is to Jean and other characters can be a little on the nose.
In fact, Scott's feelings for Logan were blatantly pointed out in Astonishing X-Men #13, when a Cassandra Nova-influenced Emma Frost tried to drive Cyclops away by showing him just how much he envied Wolverine, with a telepathic illusion that would give Freud a field day.
Meanwhile, Wolverine has long expressed envy of his fellow X-Men's relationship with Jean, as well as many other aspects of Scott's life dozens of times; he's even been known to (sarcastically) call Scott a 'pretty boy.'
Aside from this, his nearly unshakable belief in Cyclops's leadership abilities, Logan's trust and desire to protect him from physical dangers and getting his hands dirty with killing has been enough for many fans to speculate about the nature of his feelings. It wouldn't be the first time Wolverine's potential interest in men has been indicated, either; one famous example is Esad Ribic's suggestive Wolverine cover featuring a naked Nightcrawler.
Though some fans may think a polyamorous relationship between Wolverine, Cyclops, and Jean Grey is out of left field, decades of evidence suggests otherwise.