Britney Spears' younger sister, Jamie Lynn, celebrated her 17th birthday in the company of her boyfriend and baby-daddy, Casey Aldridge, 18, shopping at department store JC Penney in Mississippi.

The two soon-to-be parents are rumored to be engaged after Jamie Lynne was spotted wearing a shiny diamond ring on her hand. Sources close to the couple also claim that wedding plans are already under way.

"Jamie Lynn and Casey are officially engaged," a close friend of the teen couple confirmed to OK! magazine. "They’re committed to each other and anxious to be the best parents they can possibly be, and also the best husband and wife they can be to each other."

However, Jamie Lynn's mother, Lynne Spears isn't entirely convinced her youngest daughter's marriage is a good idea and insisted that the "Zoey 101" star and her fiancé sign a prenuptial contract before getting married.

"The contract is already drawn up and ready to go. Lynne’s not sure marriage is a good idea, but she’ll go along with that if that’s what Jamie Lynn wants, as long as Casey signs the contract," a source was quoted by In Touch Weekly as saying,

"Lynne is keeping an eye on him. He doesn’t seem as committed to the relationship as Jamie Lynn."

In the meantime, Britney, who is planning to release her own her own clothing line, was spotted at Ed Hardy's corporate offices in Culver City, California on Thursday to meet with designr Christian Audigier and while she was there she also picked out some Ed Hardy duds she liked, including some birthday presents for her younger sister.

"Britney came in to talk with Christian about working on a line together," Ed Hardy's Marissa McMillion was quoted by Star as saying.

"She was really nice to everyone in the office. Her mom was with her and Britney asked us to send some clothes to her sister Jamie Lynn for her birthday tomorrow," she added.

Britney's selection of things picked up for her sister included several Christian Audigier handbags, scarves, and Crystal Rock T-shirts. She also snagged some items for her father and brother.

"Britney's favorite piece was a leopard hoodie and she loved the sunglasses — she put them on immediately. But most of all she was a fan of Christian Audigier's own line."