Cressida Bonas supported her half-sister Isabella Branson's latest acting venture on Wednesday night.
The 25-year-old was joined by her extended family at The Tricycle Theatre in London to see 34-year-old Isabella perform in The Colby Sisters Of Pittsburgh, Pennsylvania.
Cressida and Isabella's mother Lady Mary Gaye Curzon was also in attendance as were Isabella's husband Sam Branson and her mother-in-law Joan Templeman.
Isabella Branson and Cressida Bonas
Fresh from the stage, Isabella joined her relations at the show's after party to celebrate.
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The model and actress, who previously starred alongside Kristen Dunst and Simon Pegg in How to Lose Friends and Alienate People, sported a summery sleeveless jumpsuit for the occasion.
Left to right: Joan Templeman, Cressida Bonas, Sam Branson, Lady Mary Gaye Curzon
Cressida, who recently made her own acting debut at the Hay Festival in Wales, wore a simple black dress, metallic gladiator sandals and a denim jacket.
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The socialite held her blonde locks in place with a black headband and accessorised her outfit with gold hoops earrings and numerous rings.
Cressida with her brother-in-law Sam Branson
Prince Harry's ex posed with her brother-in-law Sam, whose father is business magnate Richard Branson, who looked dapper in a pink blazer, blue T-shirt and grey jeans.
Isabella and Sam tied the knot in March 2013 in an opulent ceremony attended by Princess Beatrice and Princess Eugenie. Talented Cressida serenaded the newlyweds at the wedding, performing a moving love song which brought her sister to tears.