Blake Shelton is a "fun" father figure to Gwen Stefani's three sons.

Blake Shelton

Blake Shelton

The 43-year-old country star often helps raise Gwen's sons - Kingston, 13, Zuma, 11, and Apollo, five - and whilst he wants to remain respectful to Gwen's ex-husband Gavin Rossdale, who is the father of her kids, he's also helping to show the boys a "life filled with adventure".

A source said: "He's so fun and has shown Gwen's kids another side of life filled with adventure. The boys have really grown immensely by spending time with Blake."

Blake, Gwen, and her sons often head to Blake's ranch in Tishomingo, Oklahoma, on weekends and school breaks, where the boys are keen to get their hands dirty and spend time in nature.

And it's not just Gwen's sons that Blake has been a good influence on, as sources say the 'Hollaback Girl' hitmaker has been "much more relaxed" since starting a romance with the 'Voice' coach four years ago.

The insider added to People magazine: "They're all very like-minded and comfortable with each other. [Gwen] is much more relaxed and enjoys life more. Gwen has changed a lot since she met Blake, and it's all for the better."

Meanwhile, Gwen recently gushed over Blake's ability to be a "good" father figure, as she said he's more than happy to take on more responsibilities.

The 50-year-old singer said: "He is a good dad, actually. He's been helping me out a lot. I literally get to the point where I'm like, 'You gotta get home - I need help!' It's hard. I got three boys."

And Gwen also said dating Blake has been a "healing" experience.

She added: "I feel as if I spent the last four years healing - you know, trying to build my life again. Having a best friend like Blake to help me do that has been one of the greatest gifts."