Backstreet Boy AJ McLean Checks Into Rehab Backstreet Boy A.J. McLean has checked himself into rehab again.TMZ reports:One source tells TMZ McLean has been “out of control” in the last few months because of substance abuse, and it was interfering with plans for the Backstreet Boys’ upcoming tour with New Kids on the Block.Sources say on a Backstreet Boys cruise last month … A.J. appeared under the influence much of the time.McLean has battled addiction for years. He was in rehab in both 2001 and 2002 for alcohol and cocaine abuse.On January 9 McLean hinted the news on his Twitter account tweeting: “I love u all and wish me luck! I start my sober journey tomm!”Then following up on January 10 is tweets: “See u on the other side!”Get well A.J.!