"It was basically to do with kids - she wanted a baby and I didn't," Mark disclosed to the
Sunday World last night.
And in a remarkable insight into one of Ireland's most-famous families, Mark detailed the fall-out from the marriage-break up, admitting that Conor and others could see the split coming a long time ago.
"We almost made it to our four-year anniversary - which is a long time to be married in this day and age," he laughed.
Dubliner Mark (45), who has twin 20-year-old daughters from a previous relationship, said the marriage stopped working.
"The life we were living together it just wasn't working. It wasn't for me and it wasn't for her. She wanted to do one thing, and I wanted to do the other and that's it.
"We're not talking, but we're not fighting either. We were in contact until around Paddy's Day and then we had a row and we just don't talk since. It is what it is. We are just two different people."
Mark added that Aoife (35) has been living in her parents' house since Christmas, while he is still living in the house they used share in the grounds of the K Club in Co Kildare.
He admits that Conor and others knew the relationship had broken down long ago.
"We spent time with each other for the Christmas just for family sake, but since November we are living apart and that's really it."
Aoife is one of three children of Tony and Margaret McGregor - Conor (33) being the youngest, and hairdresser Erin who became a panto star and featured on RTÉ's Dancing With The Stars.
Make-up artist Aoife met Mark through mutual friends over 10 years ago and they hit it off straight away.
When they got engaged Mark went down on bended knee before a helicopter arrived and whisked the happy couple off to celebrate at the luxury Powerscourt hotel in Co. Wicklow, where they eventually got married on New Year's Eve 2016.
Many of the public would be familiar with Aoife from her infamous run-in with her dog groomer, which went viral after she went berserk and fumed "the neck of ye."
Mark declined to comment on that audiotape and in fact he is bighearted in his attitude to his estranged wife.
"Let her move on and be happy and have a baby," he valiantly insists. "I don't want to have a baby.
"It was cool at the start when we were together and then got married and all. Then you just realise I'm a bit older than her. There's a 10-year gap between us.
"I wanted to live a simple life, and she spends most of her time travelling the world minding Conor's kids with Dee, so we were mainly apart for most of the year - which put a strain on her marriage.
Mark works as a mini-digger operator and has changed his life around since he served time for dealing in cannabis.
Gardaí raided his then home on February 16, 2009. During the search officers discovered two kilos of cannabis herb on the property, with a street value of €40,000.
Mark was charged with possession of the drug for sale and supply, at Dublin Circuit Court the following June.
He received a total sentence of six years in prison in connection with the raid. However, two years of the sentence were suspended and with 25 per cent remission applied Mark walked free from Wheatfield jail in June 2013.
"Its 'Mark Elliot the drug dealer and he was 'convicted and sentenced in Wheatfield'," fumes Mark about coverage of him previously. I live in the K Club and all my neighbours know me and know I'm a good bloke. What happened was in the past."
Mark confesses he lied on American immigration forms that he had no criminal convictions so he could go see McGregor fights in Las Vegas.
On several other occasions he even travelled over on Conor's private jet on excursions with the sports star.
But four years ago, Mark was one of over 50 McGregor fans who were turned away at Dublin Airport by US immigration officials, who deemed them persona non grata for access to America.
Fashionista Aoife is currently Los Angeles, where she has joined Conor and his fiancée Dee Devlin and their three children and has recently been flaunting her new life on Instagram.
The blonde hinted in recent posts that she had split from Mark.
"Swapped the Diamond on my Finger for Diamonds on my shoes @machandmach till death do us part," Aoife wrote in a snap of a new pair of stilletos.
And in her most recent picture, Aoife showed off her stunning figure as she posed for a black-and-white snap.
"I ain't looking back…but here's a throw back," she captioned the post.