The 29-year-old singer - who is one half of the duo along with Ben Earle - and the former 'The Only Way is Essex' star both auditioned in 2013, and shared a bedroom together whilst they were on the show.
Crissie was tipped to win, but was knocked out early on, whilst Megan, 25, made it all the way to boot camp, but both stars have gone onto to forge successful careers.
They are set to perform at British Summer Time Hyde Park on July 13, supporting Canadian superstar Michael Buble.
Speaking exclusively to BANG Showbiz ahead of the festival, Crissie said: ''I was actually on 'X Factor' with Megan in 2013.
''We shared a hotel bedroom for one night.
''I remember the show saying there was only room for one country singer.
''I was like, 'Why is that?'. There is definitely room for more country stars.''
The 'Stay The Night' hitmaker is glad that Megan is finally getting to live out her dream and hopes to catch up with her at the festival.
She added: ''It's cool that she is back doing what she was excited to do.
''I haven't spoken to her in ages so I will definitely speak to her on the night.''
The Shires and Megan join Van Morrison, pop vocal group Bananarama, indie rockers The Feeling and more in supporting Michael Buble at Barclaycard presents British Summer Time Hyde Park on July 13.
Meanwhile, most festivalgoers are planning to shun social media in order to be ''in the moment'' and get the most out of the events this summer.
Research conducted as part of Barclaycard's Summer of Goosebumps Study, a year-long exploration into Brits' experience of live entertainment and the science behind music and emotion, found that 71 per cent plan to indulge in a 'digital detox' and ditch their smartphones altogether, while almost a quarter hate people filming the gigs on their phones.
A further 62 per cent report feeling that social media is a distraction which hinders their festival experience and instead will opt to step outside their comfort zone at this summer's events to make new friends.
Healthy foods are a new must-do for almost half of those surveys, with more opting for salads and smoothies or vegan dishes over burgers and hot dogs.
And music and food aren't all that people want from their festival experience, as 30 per cent now look to take part in activities such as yoga, meditation and mindfulness to enhance their overall enjoyment during live events.
Aspiring headliners will have the chance to feel like a true music star and complete their own stage dive as part of the new Perk Park, an exclusive place for customers at Barclaycard presents British Summer Time Hyde Park which kicked off on Friday (06.07.18).