Billy Joel wasn't the only celebrity to tie the knot this Fourth of July weekend.

After months of playing coy about whether they're married, "That '70s Show" co-stars Mila Kunis and Ashton Kutcher have made their union official, a source tells People magazine, which broke the story Sunday. Us Weekly said it had confirmed the news Monday morning.

Kunis, 31, and Kutcher, 37, met on the set of the Fox sitcom in 1998, but only began dating in 2012 after he and Demi Moore split. They got engaged in February 2014, and welcomed a daughter, Wyatt, in October.

In January, Kutcher sparked rumors of a secret wedding when he posted a Facebook photo that read "Happy New Year, the Kutchers." Two months later, when "Late Late Show" host James Corden asked Kunis if she was married during an appearance on his show, she replied, "maybe."

This is the first marriage for the "Ted" actress. Kutcher's divorce from Moore was finalized in November 2013.