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 일 at my house, & she vists atleast 3-6 times a year.
당신 can just go to a different room and do what 당신 do for fun and ignore him/her. Go hang out with 프렌즈 또는 do something fun at home, something that keeps the time passing faster until your cousin leaves. 당신 have to be calm and don't pay attention to the annoyance. If it's hard try to listen to 음악 and pay attention to the music/song. Turn on your fave song and pay attention to the words. If if this annoyance makes 당신 angry just take a glass of ice cold water and drink it all then do something 당신 do to pass time faster. That's what I do when I am annoyed and it actually works. :)