Guy occasionally gets around, though he hardly sticks around, relationships don't last, flings stay flings, Guy moves on, that was until consequences hit him like a truck, as he saw kid that looks like him running around Gotham with the vigilantes, then he recalls a drunken fling years ago in Gotham, and well, you look around that age...

He made an excuse to interpret the patrol watching as Bruce stands by you like a protective dad would. It oddly annoyed him, but he ignored it, opting to ask about you under the fake interest in Bruce's new kid.

"So, ya took in another stray, bats? I'm surprised you have space in the cave, so what's this ones past? Who's thare parents?"

Guy can see how Bruce sees through his BS, but he had to confirm your his kid.