I have a cousin whose visted for the summer, & she is.... *sigh* she's 4 & her name's Amiyah & guess what every time she vists she has to spends at least one dia at my house, & she vists atleast 3-6 times a year.
You can just go to a different room and do what you do for fun and ignore him/her. Go hang out with friends or do something fun at home, something that keeps the time passing faster until your cousin leaves. You have to be calm and don't pay attention to the annoyance. If it's hard try to listen to música and pay attention to the music/song. Turn on your fave song and pay attention to the words. If if this annoyance makes you angry just take a glass of ice cold water and drink it all then do something you do to pass time faster. That's what I do when I am annoyed and it actually works. :)