United Kingdom, June 15 -- Sienna Miller's sister has confirmed the actress' engagement.

It was reported last week that the Factory Girl star was set to marry boyfriend Oli Green after she was pictured in Spain wearing a huge diamond ring, and now fashion designer Savannah Miller has revealed their whole family are delighted with the news.

Savannah told Britain's HELLO! magazine: "We're all over the moon. It's the happiest news, and it was beautiful, the whole thing. I can't express how happy I am for her."

Sienna and Oli welcomed their second child together into the world earlier this year, a sibling for their two-year-old daughter and the 44-year-old actress' oldest child Marlowe, 13, who she has with former partner Tom Sturridge.

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