Brother & Sister Start To Sing Then Uninvited Dancer Springs Out Without Them Knowing

Every family has that one sibling that is crazier than the rest. Whether they're always trying to make everyone laugh, or always getting into trouble from acting out – one thing's for sure and that's that you've gotta love 'em!

When siblings Kate and Liam decided they wanted to sing a duet together they both prepared and practiced the song "Think About You" by Lady Antebellum.

Only when the camera stopped and they looked over the footage after their performance they realized they weren't the only one's performing in their video.