The Alfie star ended her on/off relationship with actor Balthazar Getty earlier this year (09) and has moved on by getting close to British DJ Slinky Wizard, real name George Barker.
Savannah, who set up fashion label Twenty8Twelve with her famous sister, went on a string of dates with Barker seven years ago, according to Britain's Mail on Sunday newspaper.
The paper reports they remained close after the split, with Savannah eventually pairing her ex with her younger sister.
A source tells the publication, "Savannah introduced George to Sienna and thinks that he's perfect for her. He's funny, charming and naturally hippie at heart. He loves to party and so does Sienna, so they are well suited.
Sienna has already introduced her new beatmaker boyfriend to the rest of her family, reportedly taking him along to a lavish poolside party in Ibiza for her step-mother Kelly Hoppen's recent 50th birthday.