He's one half of the TV presenting duo with Ant McPartlin.
Yet Declan Donnelly,42, is said to be torn between supporting his best friend and Ant's estranged wife Lisa Armstrong now that the pair have announced their plans to divorce.
A source told The Mirror: 'Dec will always stand by Ant, but over the years he has, naturally, become very good friends with Lisa, and his wife, Ali, is also very close to her.'
They added: 'He feels very much torn and it’s a tremendously difficult situation for all concerned.'
Meanwhile, Dec’s wife Ali Astall is said to have become 'a shoulder to cry on for Lisa'.
MailOnline has contacted Dec's representatives for comment.
Ant, 42, and Lisa, 41, announced their plans to divorce last week, with Ant's spokesman confirming to MailOnline on Saturday: 'In response to the recent speculation in the media, Ant is very sad to announce that, after 11 years, he is ending his marriage to Lisa McPartlin.
'Ant asks for privacy at this difficult time, for both himself, Lisa and their immediate families. No further statement will be made.'
Ant and Strictly Come Dancing make-up artist Lisa have known each other for 23 years and tied the knot in 2006.
Ant has been living apart from partner Lisa, having moved out of the £6million property they share last year following his stint in rehab for an addiction to painkillers.
He had spent the last two months filming in Australia for ITV reality show I'm A Celebrity, but Lisa was unable to join him overseas, due to her commitments to BBC One's Strictly Come Dancing.
At the time, Lisa dismissed claims that this made her 'estranged' from husband Ant, explaining that she had not been out to Australia with him for 10 years.
Ant and Lisa's divorce could reportedly cost the ITV star, whose net worth is estimated at £62million, a grand total of £31million.
If it goes ahead, it will be among the largest divorce settlements paid by a UK celebrity in history.
