The "Came Here to Forget" hitmaker sought solace in Stefani when he split from Miranda Lambert, only to find out she was also going through a divorce from Gavin Rossdale., reported Aceshowbiz.
"We were starting 'The Voice' last year, and I had to sit down and go, 'Look, by the time this thing airs, my life will have completely changed, and we need to talk about this now because it may affect what we talk about on the show.'
"I just felt like there doesn't need to be secrets. And then the same thing [happened] with Gwen. It was like, 'Here's what's going on, this show ain't gonna air until three months from now, so let's get this talked about right now'," he said.
"That's how we even found out what was going on. And we just started to develop a friendship after that. And it took awhile, because it's chaos. But just over time, seeing each other a lot at work, it just kind of developed into that.