Imagine person A of your OTP tricks person B into going into a closet with them (or any small enclosed space), and closes the door. They then start softly making out. Little does B know, A forgot to lock the door.
Person C opens the door, looking for something in the closet, having no idea that A and B were making out in there. A and B simply stare at C, in the middle of a kiss, as C just shrugs and reaches past them to get what they came for off of a shelf, before closing the door and leaving.
A and B are confused, but nonetheless, they continue to make out once C is gone.
A is Gavin, B is Nines, and C is either Hank or Fowler.
YOU CAN NOT CONVINCE ME OTHERWISE