No longer having an arm wrapped around a cute blonde or no more wandering eyes across the room. Cheeky smiles bordering on performative and hands are always almost occupied.
At first, no one notices. It's Bruce freakin' Wayne. He's probably hiding a scandal behind those grins and laughs.
But then.. his kids notice he's more distant in his outset personality. More subtle implication he's not interested when he casually steps back from a determined woman, champagne gracing his lips. They think it's just an off night, right? But eyes become softer, shoulders aren't so tense and he's got that faraway look in his eyes that seems to be everything he warned them about.
But he's batman, so they can't just..ask. Any subtle implication gets brushed with the same undertone or a grunt. No matter how many tracking devices, microphones, or whatever they can get their hands on can suffice.