A source tells PEOPLE the couple got engaged a week ago on her 36th birthday while the two were in London.
Jonas closed down a Tiffany store in New York City to buy an engagement ring, according to the insider.
“They are so happy,” the source says.
Reps for both stars did not immediately respond to PEOPLE’s request for comment.
A Jonas source tells PEOPLE the singer is “very, very happy.”
“His friends and family have never seen him like this, and they’re all really excited for him. He’s definitely very serious about her,” the source says.
This article originally appeared on PEOPLE