The 27 Club—also occasionally known as the Forever 27 Club, Club 27 or the Curse of 27—is the concept that many popular musicians have died at the age of 27, often as a result of "precipitous lifestyles that made them candidates for early self-destruction."  The deaths of some prominent musicians at age 27, such as Brian Jones, Jimi Hendrix, Janis Joplin, Jim Morrison, Kurt Cobain and Amy Winehouse have been linked to this idea.

Source: http://en.wikipedia.org/wiki/27_Club

Brian Jones was an English musician and a founder member of the Rolling Stones. (Cause of Death: Drowning in his swimmingpool, while his liver and heart were heavily enlarged by drug and alcohol abuse) 

Jimi Hendrix was an American musician and singer-songwriter. (CoD: Respiratory arrest caused by alcohol and barbiturate overdose and vomit inhalation.) 

Janis Joplin was an American singer and songwriter.(CoD: heroin overdose)

Kurt Cobain was an American singer-songwriter, musician and artist, best known as the lead singer and guitarist of the grungeband Nirvana. (CoD: Suizide)

Amy Winehouse was an English singer and songwriter known for her powerful deep contralto vocals and her eclectic mix of musical genres including R&B, soul and jazz. (CoD: Alcohol overdose)