There ought to be an underlying romantic tension to their relationship, but it should be one way and not reciprocated. A college age Jean is going to have the exact same physical appearance that Logan was deeply attracted to for all those years. Old Man Logan would still be in love with young Jean Grey because of course he'd be; I can't think of any biological or psychological reason he wouldn't be.
But why would a gorgeous redhead in the prime of her youth be attracted to a senior citizen whose mutant healing factor can't hide his wrinkles any longer? And Logan would realize as much, creating an interesting dynamic: He always loving her in silence and long suffering, and she (as a telepath) aware of his feelings for her but unwilling to break his heart.
Despite the super-powers and time travel, such could prove one of the most realistic relationships in comics.
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