If their child walked in on them mid-dance practice, BTS would probably be completely shocked. They'd be like, "Oh no, our secret's out! Our kid knows we're actually not that cool!" And then they'd all burst out laughing because, let's face it, it's a pretty funny situation.
Their reaction would likely involve a lot of denial and blame-shifting. "RM made me do it!" or "Jin started it, I swear!" would be the cries echoing through the room. Meanwhile, their child would be standing there, totally confused, wondering what's going on and why the room is filled with so much laughter.
Suga would probably just shrug it off and be like, "What's the big deal? I'm a rapper, I can do what I want!" But deep down, he'd be secretly embarrassed because, well, who wants their kid to see them in such a vulnerable state? The rest of the group would just be teasing him mercilessly, making jokes about his "dad moves".