Jean-Luc/Jack/Beverly? I guess this is kind of tragic so you can go for either a happy or a tragic scenario...or both?
Yes, yes, yes! Thank you, I love them! Two things I will always, always ship are best friends and tragedy.
So as I recall, Jean-Luc was friends with Jack first, along with Walter Keel, who introduces Jack to Beverly. So first we get “I’m a grown man but who’s this girl stealing my boi” feels. Then we get “I hate how adorable they are I am feeling a lot of feelings mainly jealousy and I don’t even know which one I’m more jealous of” feels. At some point Jean-Luc definitely has “why didn’t Walter introduce her to ME” thoughts that he feels terribly about because Jack is so happy. As for Beverly, she’s intimidated at first, Jean-Luc is so reserved and intense. She wonders how they are even best friends. But she comes to respect him and then care for him as Jean-Luc and not just Jack’s (weird) friend. If she ever had doubts about the wedding she’d seek him out. And he’d support into going through with it. There are feelings. They both suppress them for Jack’s sake. They prioritize Jack because he’s the best of them. He’s a bright shining star they are lucky to orbit. And then he dies and everything falls apart. They want to cling to each other but it feels disrespectful. They both pull back and get stuck there. For years. All this is basically canon.
There are plenty of moments where things might change. Jean-Luc and Jack have a relationship prior to Beverly’s introduction. This intensifies the jealousy, but then Jean-Luc falls in love with Beverly, too. He and Jack get into an argument over nothing, Jack accuses him of being jealous of Beverly, of hating Beverly, and Jean-Luc yells that he has no idea what he’s talking about and Jack’s eyes go wide because he realizes Jean-Luc loves HER and he’s so hurt that Jean-Luc cares for her and cares for her more than he cares for him and Jean-Luc loses it because how can he not understand that he’s in love with BOTH of them and they get to be together but he is completely alone???? They stop shouting and stare at each other and then Jack apologizes and suggests maybe Beverly is into that? And Jean-Luc is like, are YOU into that? And Jack is, totally, and Jean-Luc is curious despite himself but thinks asking her is a terrible idea, but Jack ignores him. And she’s into it.
Or, Jean-Luc has been in unrequited love with Jack prior to Beverly’s introduction. This intensifies the jealousy and the resentment and he spends a lot of time hating her. But Jack loves her, and she makes him happy, and Jean-Luc wants him to be happy so he tries to get along with her. And it turns out she’s pretty great. And one night, they are all talking and Beverly accidentally (maybe) lets it slip that she knows that Jean-Luc has a crush on Jack and Jack is like ha ha ha, that’s absurd but Jean-Luc is glaring at Beverly with a burning rage and then he stomps off and Jack is like what? And Beverly says she’ll fix it and runs after Jean-Luc. And she apologizes but says he shouldn’t hide his feelings and she’s not a monster she really loves Jack and she thinks he loves her too and Jean-Luc is like Of course he loves you, you are annoyingly loveable and she’s like Thanks? And he’s like look, I honestly want you both to be happy but sometimes it’s hard because I’m all alone. And she tells him he’ll only be alone if he keeps pushing them away and returns to Jack. Things are awkward for a few, but eventually they find a rhythm and one night Beverly invites him to stay past dinner and drinks and not on the couch and Jean-Luc looks at Jack and Jack looks at Jean-Luc and then they both look at Beverly and Beverly takes their hands and tugs.
(In either of these scenarios, Jack’s death and their subsequent separation followed by years of dancing around each other is even more tragic. He’s not just a ghost standing between them, he’s their missing piece.)
Or, Beverly is on the Stargazer with Jack and Jean-Luc and they are the absolute best command team in the Fleet and no one dies and when Jean-Luc is offered Enterprise Jack and Beverly follow him there instead of accepting a separate command because they want to start a family and the Enterprise-D exists for that. They have their own suite of quarters and coparent little Wesley Stargazer (three last names is too many). Since no one dies Wesley gets a little sister, too, Keely Stargazer.
Honestly, I really want to know more about Jack Crusher, Jack & Jean-Luc, Jack & Beverly, and Jack & Jean-Luc & Beverly. There are some books but none of them has ever truly sold me. Q-Squared comes closest because it claims that every universe bends to make certain Jean-Luc and Beverly end up together (so in the one where Jack lives, Wesley dies) and that’s the kind of relationship intensity I live for. But Jack is still screwed over and it’s not fair, he should matter.