The pair met at the Pride Of Britain awards in 2009, and went on to confirm their engagement in 2011.
In a chat in the latest issue of Red magazine, Frank reveals that his relationship with Christine has made him happier, expaining: “She’s made me content. ‘That sounds soppy, but I’ve been very happy since I’ve been with her. Our personalities are very similar. I’ve got a lot of respect for what she says - she’s sharp.
“I bounce my problems off her, and I’d like to think I help her with her stuff, too.
“People say opposites attract, but when you live together, you need to be harmonious, and she’s my best friend.”
He also discusses how Christine has been a great step-mum to his two young daughters, Luna and Isla, whose mother is the Spanish model Elen Rivas, who he was with for seven years until they eventually split in 2011.
He says: “It’s certainly helped me having Christine and the bond that has grown between her and the girls.
“[They] will now gang up on me. For me, that’s great, because going into a relationship, the step-parent role is hard.
“And it does me a favour, because I had a year of being a single dad and it was tough.”
It was recently claimed that England coach Roy Hodgson had banned all footballers’ wives and girlfriends from attending a World Cup mini-camp in Miami starting next month, meaning the pair may have to get used to spending some time apart for the time being.
Read Frank’s full interview in the new issue of Red magazine, on sale 30 May. Also available in digital edition on Apple Newsstand. Click here for more content.