The rope is no wider than his thumb, the height is 25 stories up and the length is five city blocks, but what really concerns aerialist Nik Wallenda about his high-wire walk in New York on Sunday is his sister.

Wallenda and his sister, Lijana, plan to walk 1,300 feet (396 meters) across the city's busy Times Square on Sunday in a live television event that has been six years in the making.

The walk will mark Lijana's first high-wire stunt since an accident while rehearsing an eight-person pyramid in 2017 that broke every bone in her face.