The baby your mom gave birth to who isn't you. The one who is sometimes a curse, and sometimes a blessing.
Person 1: My younger sister photobombed me and now it's a meme, and a sticker!
Person 2: It's a gif, too!
Person 1: Oh boy, there goes the rest of the schoolyear.
Person 1: Who spread this rumor about me!?!?!?
Younger sister: Kat!
Person 1: Thank you! I'll tell her to take it down.