So, I saw your post about Sam finding out that his least favourite coworker is now his nephew and lemme tell you, it is l e g e n d a r y. Yet, I offer you a counterproposal: Sam and May or Sarah and May are dating and neither Sam or Sarah know Peter is Spiderman. So at the first joint family dinner with Sarah, Sam, May and Peter, Peter is super quiet and awkward because he knows he annoys Sam in the suit, he doesn't want to annoy Sam out of the suit and mess it up for May. Cue Sam being confused bc he's heard so much about Peter, either from May herself, or Sarah, depending on who's dating May. (May just loves bragging about her incredible nephew okay?). So he tries to bond with Peter, who opens up a bit, but is still super shy and awkward. Obviously, Sam grows fond of him, because how couldn't he? Eventually, he finds out that Peter Parker and Spiderman are the same person, and he's shocked bc they're so different? Like Peter is shy, clumsy and oblivious and Spiderman is witty, even in the face of Danger - once he saw him crack a joke with a gun pointed in his face. He's just unable to connect the two in his head. But then Sam takes him out for ice cream one day and suddenly Peter just throws himself in front of a kid, pushing him out the way before he could get run over. Peter's injured, and that's when Sam realised. It's not so weird that Peter Parker and Spiderman are one and the same. Spiderman is loyal, selfless, kind. That doesn't come from the suit - that's all Peter. He gets on with him much better after that, even if he never lets the car incident go.
MY FRIEND WE ARE ON THE S A M E WAVELENGTH!! YOUR MIND!! because - mild spoiler alert for my upcoming sarahmay // sambucky fic - in my sm // sb fic, sarah is not going to learn peter is spider-man by the end of the story (sam already knows his identity because i like the hc that he and bucky kind of look after peter in the field/training when they can now that tony is gone; the fic is endgame-compliant and ig either set before ffh or just not compliant with ffh, lol). why have i done this? because i want to explore in future fic(s) how sarah discovers that peter is spider-man, not dissimilar to the process of realization for sam you describe here!! great minds think alike!!