you had a sister/brother and you two where in the same class and the rest of the class didn't know you two where siblings... Yet-... One day you two where goofing around in the dorms and forgot everyone was still there. You where to busy playing around

Bakugou:CAN YOU TWO SHUT THE FUCK UP FOR ONE'S!?

Deku:kachan calm down there just playing around-....

Kirishima: ya what's the problem Bakubro?

you and your sibling laugh nervously