The 21-year-old confirmed the surprising news yesterday with an Instagram picture of her and Watson hugging while flashing her ring finger.

The caption: "Guesssss what?"

This will be the first marriage for Jamie Lynn Spears, who was previously engaged to Casey Aldridge, the father of her four-year-old daughter Maddie.

Jamie Lynn split with Aldridge in 2010.

Britney Spears, meanwhile, recently parted with fiance Jason Trawick and is now dating David Lucado, a totally random but very nice-seeming fella.

Congratulations to Jamie Lynn and Jamie - and follow the jump for a bonus pic of Spears' engagement ring. As she captioned the pic, "He did good."