This is the moment brother bears play with each other for the first time in 17 years at Yorkshire Wildlife Park

Kai and Riku have spent 17 years living next to each other, but have never had contact with each other - until today.

A spokesman for the park wrote on Facebook: "Earlier today, our Rangers introduced brother Kai and Riku together for the very first time. After 17 years of living next to each other, but never having been in contact with another bear, it was a fantastic moment. The boys will be out in the reserve together all day today."

These lovely photos show the siblings, who are endangered Japanese bears, rolling around together in the reserve and playfully biting each other. They even appear to be smiling.

The pair are two of four brown bears who were brought from Japan to a new life in Doncaster earlier this month.

Riku, Kai, Hanako and Amu had been living in outdated cages at the Ainu Cultural Museum, on the island of Hokkaido, and urgently needed new facilities, according to staff at the Branton-based park.