Katy Perry's Part Of Me film will be a family affair - the pop star is including her older sister in the upcoming 3D movie.

The California Gurls singer is set to give fans a glimpse into her private life by sharing rare footage of her 30-year-old sister Angela Hudson, who bears a striking resemblance to the star and works as her assistant.

In a new promo for the documentary, the duo can be seen challenging Hudson's fear of heights by taking a bungee jump together and enjoying a trip to a water park.

Hudson also discusses their working relationship, explaining, "We always kind of had this deal that when (Perry) made it big, I was going to work with her and we were going to be together...

"My sister, not only does she like to work hard on tour, she likes to play hard on tour. Any time we go to a city where we have a day off, she always likes me to explore something fun with her."

Part Of Me also features home video footage of the pair performing side-by-side in a choir as youngsters.