It's not mathematically possible
Kal'dur said, "Who exactly is a Wayne?"
Kara said, "This stupidly rich celebrity family out of Gotham. Bruce Wayne is infamous for adopting a lot of kids. But we can't all be dating a Wayne, right?"
"It's not mathematically possible," Kon began. "Is it?"
The silence in the room was deafening. Roy seemed to be counting his fingers.
Or
Roy Harper makes an off-hand comment about being invited to the Wayne Holiday Gala, and Artemis mentions that her and Wally have also been invited to the Gala. It doesn't take long for Jon, Kon, Kara, Steph and Clark to join in. They can't all possibly be dating a Wayne, right?
(Tagged mature for swearing and spice but no smut)