1. Congratulations <3

  2. Happy Anniversary to you! I hope you will be together for the next 20 Years or longer. You are soooo amazing. Love to you

  3. Happy Anniversary!!! :)

  4. Happy 21th birthday backstreet!
    Thank you for always being there with your lovely music the past 21 years . I am a fan of Nick since we've got it goin on . By than i was 7 years old today i am 26 years.
    I love you Nick now more than ever .
    Keep the backstreet pride alive !

  5. Happy Anniversary!! From the moment I heard Quit Playing Games I became a fan. Your music has helped me get through So Much & when I need you guys you're Always there with new music & tours. Thank you guys for so many yrs of Great Memories!! I will Always love & appreciate you for all you do for your fans. You guys are the best!! I will Always KTBSPA!!!! #21YearsOfBsb

  6. Happy Anniversary - Love how after all these years you still bring enjoyment to fans of all generations - Love and all the best to you all - your families and your fans across the globe - Your music will live forever -

  7. KTBSPA!!!!!
    --Beijing China

  8. Congratulations :)

  9. Congratulations on 21 years! What an achievement! You guys have been a massive part of my life and I thank you for that. Here's to 21 more! x

  10. Extra special cause it's on Easter Sunday.