I just read this book called 'Maybe Someday' by L.J. Shen last week that accidentally plunged into this exact minefield, and wow, it left my stomach in knots for days. The book wasn't about that, but there was this secondary plotline with the protagonist's friend who harbored feelings for her best friend's adult son, and the sheer number of conflicting emotions packed in there was incredible.
It's not just about attraction crossing a generational line—though that's a huge part of the initial ick factor and the social taboo that makes your palms sweat. The real gut-punch is the dual betrayal. You're potentially betraying the trust and friendship of someone who saw you as a peer, a confidant, by viewing their child, this person they raised, in a romantic light. And simultaneously, you risk betraying the 'son' figure too, because your history with his parent inevitably colors the relationship; you're not entering it as equals, you're coming in with a pre-existing power dynamic and a lifetime of context he wasn't a part of. It sets up this awful triangle where honesty seems to guarantee you lose at least one of them, maybe both.
That particular story handled the fallout through a lot of secret pining and missed connections, which honestly felt truer to life than some grand confession scene. The fear of being seen as predatory or pathetic by your best friend, the worry that you're misreading youthful admiration for something more, the guilt that even having these feelings feels like a violation of an unspoken rule—it all builds this pressure cooker of anxiety that's weirdly compelling to read.