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