Kate Middleton‘s brother is getting hitched.

James Middleton on Sunday announced his engagement to French girlfriend Alizee Thevenet by sharing an online photo of the couple beaming — with her wearing a sapphire sparkler.

“She said OUI,” the 32-year-old wrote on Instagram. “Our secret is out but we couldn’t be happier to share the news.”

The younger brother of Prince William’s wife was first linked to the 30-year-old financial analyst last year when she accompanied him on a Middleton family vacation for Christmas, the Daily Mail reported.

The pair went public this summer when Thevenet joined the Middleton brood again to attend the Wimbledon Tennis Championships in July.

In Sunday’s online post, James included a slideshow of photos of them together on his Instagram story to the song “Sexy Weekender” by Scoundrel.

“I asked @alizeethevenet a question the other day…” he wrote.