Tobey Maguire's ex-wife has got engaged

Jennifer shared a photo on Instagram of herself and the 33-year-old billionaire's son with her hand resting on his, showing off her new diamond ring.

She captioned the post: "YES!!! [black heart, infinity, sparkling star emojis] (sic)"

Jennifer - who made her red carpet debut with Geoffrey at the Baby2Baby event in Los Angeles last November - also reshared a photo from her friend Allison Wise, who had posted a photo of them together with her pal's ring on display.

Allison captioned her post: "So happy for this angel queen - my everything BEST friend who is marrying the greatest man and her should mate! I love you and can't wait to keep celebrating you both!"

Despite her own profession, Jennifer revealed she had no input into her engagement ring.

Birdie co-founder Bianca Gates had commented: "Wow!!! Huge congratulations!!! And that ring!!!?!? I wouldn't expect anything less for the jewelry queen!(sic)"

Jennifer replied: "It was allll him! Total surprise."

A host of her famous friends also offered their congratulations.

Goldie Hawn wrote: "this makes us all so happy. I love you!!!(sic)"

Olivia Munn posted: "I'm so happy for you!!"

Her sentiment was echoed by Jenna Dewan, who wrote: "I'm so happy for you my love!!!"

Both Jennifer Garner and Paris Hilton simply wrote "congratulations" with a selection of emojis, while Kelly Rowland commented: "'So incredibly happy for you!! CONGRATULATIONS!!"

Jennifer recently admitted she and Tobey - who have children Ruby, 17, and Otis, 15, together - are still very close.

Appearing on the 'Broad Ideas with Rachel Bilson + Olivia Allen' podcast, she explained: "Tobey is my best friend now. We travel together, we do every holiday together, I'm so lucky.

"I literally have the best ex-husband in the world and I hit the jackpot. I honestly don't know what I would do without him in my life. I ride for him so hard. He's so phenomenal."

Tobey is even on good terms with Jennifer's partner, but she admitted their positive arrangement is the result of "a lot of work".