Sarah Ferguson has praised her "incredible, humble" daughters.
The Duchess of York is very proud of Princesses Beatrice and Eugenie - whose father is her ex-husband Prince Andrew - and is delighted they have joined her in becoming patrons of the Teenage Cancer Trust.
She said: "The Duke and I couldn't be more proud of this moment.
"Their actions show their commitment and dedication to their grandmother and their country.
"It's so great to see them shining and I'm very, very proud.
"I think they're the most humble people I know in my life and the Duke and I are lucky as parents to have these incredible, humble children."
Beatrice, 28, who joined her mother and 26-year-old sister to visit TCT's specialist unit at London's University College Hospital recently, was pleased to follow in the duchess' footsteps and "do this as a family".
She told Britain's HELLO! magazine: "It's about supporting young people and making sure we recognise that teenagers have to go through so much - and then you add cancer on top of that."
The princesses quickly bonded with the patients they met on their visit.
Eugenie talked about her university days with 20-year-old student Elias Taylor.
She said: "He went to Birmingham and lived in a house with four boys, and I went to Newcastle and shared with seven girls. We have a similar path.
"And we were talking about the holidays we've been on.
"To be among these young people is amazing. They're all so strong."
Elias, who has leukaemia, was impressed by the royal visitors.
He said: "I didn't feel like I was talking to royalty. It was just nice having a good rapport with her. She was telling me about her nightlife while she was at Newcastle."