The couple - who met while they were both starring as coaches on 'The Voice' - first started dating shortly after their respective divorces from Miranda Lambert and Gavin Rossdale, and the early days had the feel of a reactionary fling.
In a preview for Blake's upcoming 'Sunday TODAY with Willie Geist' interview, he admitted: ''When I was going through my divorce, I hit rock bottom, just like anybody does when they go through something that devastating.
''It's a miracle that I met somebody that was going through the same exact thing that I was at the exact same moment in time...
''If Gwen and I were being honest right now, talking about this, I think in the back of our minds we both kind of thought, 'This is a rebound deal.' ''
The pair were each ''coming out of a pretty low spot in our lives'', and the 42-year-old singer admitted both he and the 48-year-old No Doubt star were ''kind of clinging to each other to get through this''.
However, their relationship has continued to go from strength to strength, and he paid tribute to the ''stronger bond'' they feel after three years together.
He added: ''But now here we are, going on three years later and every day that goes by it just feels like a stronger bond between the two of us and it constantly feels like it's going to the next level.''
His comments on their romance comes after the 'God Gave Me You' hitmaker - who was previously married twice - admitted while he thinks about getting hitched a third time to the 'Used To Love You' singer, he doesn't think it will be ''anytime soon''.
Speaking to CMT, he said: ''I think about [marrying her]. I don't think it's anytime soon or anything. The more time that goes by, I guess, the closer you'd be getting to that.''
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