Dec and his partner Ant have just signed a £40m handcuffs deal to tie them on television for many comedies to come!
Declan's parents are Anne and Alphonsus Donnelly.
Dec played the character Duncan when he was in Byker Grove, and later went on to use this name to release pop music.
In all the years Dec has been friends with Ant, they have only ever had one fight, and Ant throw the only punch.
Declan is the youngest of seven children.
He and his co-star Ant received the Show Business Personalities Award at The Variety Club Show Business Awards 2002.
With Ant McPartlin, he interviewed Prince Charles, Prince Harry Windsor and Prince William Windsor for The Prince's Trust 30th Birthday: Live.
The show that Dec and Ant both presented SMTV Live has recently been voted number 27 in the 100 Greatest Children's Television Shows that aired on Channel 4.
Dec and his presenting partner Ant did a remake of the TV series The Likely Lads which was a tribute to the show.
In the year 2005, he earned over 5 million
He had his first main staring movie role in the movie Alien Autopsy.
Along with his presenting partner Ant, he had a small cameo as himself in the British Film 'Love Actually'.
Since meeting after Byker Grove, Dec has never been on TV without his showbiz partner Ant McPartlin.
Dec has had successful shows on all the big TV stations in the UK, the BBC, ITV and CH4. With ITV bringing the most success by allowing him to create his own TV Shows, produce and write scripts.
Out of all the songs Dec released during his music career, his favorite was Shout.
At the age of only 27 he won the Lifetime Achievement Award.
He was the best man at Ant's wedding.
Ant and Dec present the UK version of I'm a Celebrity...Get Me Out Of Here, but both admit that they would never trade places and go into the Australian jungle themselves.
Dec: Touring and going to mad places. Playing the UK and all over Europe, the Royal Albert Hall and selling out in Japan
Dec: Pete and Simon have an unique relationship!
Dec: I am never ever ever being photographed in a HAT, I look like an idiot in one, I really do not suit them!
Dec: I hope everyone, once in their life can find the friendship I have with Ant.