Boo The Pomeranian -- once considered "World's Cutest Dog" -- has crossed over the Rainbow Bridge.

Boo's owner shared the news on Friday night, saying, "With deepest sadness I wanted to share that Boo passed away in his sleep early this morning and has left us to join his brother, Buddy."

Buddy crossed the Rainbow Bridge in 2017. In Friday's post, Boo's owner said, "Shortly after Buddy died, Boo showed signs of heart issues."

We think his heart literally broke when Buddy left us. He hung on and gave us over a year. But it looks like it was his time, and I'm sure it was a most joyous moment for them when they saw each other in heaven."

Boo was 12 years old.