The pop group - consisting of brothers Joe, Kevin and Nick - celebrated the late Beatles star's 70th birthday on Saturday (09.10.10), with a video message describing how much he influenced them and their career.
Nick, 18, said: "We grew up listening to the Beatles in our home, John Lennon specifically. And his words, and his lyrics, and his music spoke to many generations of people and continue to."
The trio went on to praise John - who was shot dead by crazed fan Mark Chapman on December 8, 1980 - for being "the man" and for inspiring others to live in peace through his music and life mantras.
Nick added: "It's his birthday, 70th birthday, so happy birthday, John. Thanks for the memories. Thanks for the music. And thanks for showing the world that it's time to come together and live in peace. You're the man."
In honour of the late pop star, his first wife Cynthia Lennon and their son Julian marked the occasion by unveiling a peace monument in Liverpool, North West England.
The Peace and Harmony Memorial was designed by US artist Lauren Voiers and features a brightly coloured globe with musical notes, a guitar and is topped by a dove holding a white feather.
Julian said: "We come here with our hearts to honour dad and pray for peace and say thank you to each and every one of you and everybody involved in the celebrations today."
Meanwhile, John's widow Yoko Ono and their son Sean performed as the Plastic Ono Band in Reykjavik, Iceland, and were joined on stage by former Beatles drummer Ringo Starr, before leading the crowd to sing 'Happy Birthday' to him.