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McLean has battled addiction for years, going to rehab in both 2001 and 2002 for alcohol and cocaine abuse. The news comes in the wake of their upcoming joint summer tour with the New Kids on the Block -- dubbed NKOTBSB -- with a source telling TMZ McLean has struggled with sobriety in recent months and his "out of control" behavior now threatens to derail the group's tour plans. The source went on to say that McLean appeared under the influence much of the time on the Backstreet Boys cruise last month.
While this is an ongoing struggle for the singer, it appears he made the decision willingly and with support, tweeting, "I love u all and wish me luck! I start my sober journey tomm!" Adding, "See u on the other side!"
The NKOTBSB tour will kick off on June 2 with confirmed dates running through July 30, for a total of 41 performances so far. You can see their entire tour itinerary here.
Watch the Backstreet Boys' 'Bigger' Video.