When Blake Shelton popped the question to his superstar girlfriend, Gwen Stefani, he was signing up for a commitment to more than just her. Stefani brings three children from her previous marriage to Gavin Rossdale into the relationship, meaning Shelton is soon-to-be-stepdad to 15-year-old Kingston, 12-year-old Zuma and 7-year-old Apollo.

Parenthood is a new challenge for the country star, who has no biological children himself — but he's more than ready for it. In fact, Shelton said recently that he's gotten so close to Stefani's sons that he can't imagine them not being in his life anymore.

Stefani has made it a point to acknowledge and celebrate Shelton's contributions as a "bonus dad" — on Father's Day (June 20), she celebrated all the love and care her country star fiancé brings to the family.

"Happy Father's Day to the most generous, patient, loving, funny guy I know — we love you so much," the pop star writes in a social media post, along with a slideshow of photos featuring Shelton's sweet relationship with all three of her boys.

Shelton's fatherly side is on full display in all of the pictures, which include a couple of snapshots of Stefani's youngest child tugging on Shelton's hair or sticking a finger in his ear. It's also evident that the country singer has made a point of sharing his interests with his bride-to-be's three children: One image features the crew in hunting gear, while another snap shows Shelton playing guitar for the kids.

In one particularly adorable photo, Stefani's middle son, Zuma, shows off a temporary version of Shelton's barbed wire tattoo, which he got on his left arm, to match his stepdad's ink.

Shelton and Stefani spent most of their coronavirus quarantine on his ranch in Oklahoma with her kids before moving into their first official home together, a massive California mansion, in time for the new school year. They announced their engagement in October, but they have not publicly revealed a wedding date.

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LOOK: Blake Shelton Through the Years