Pregnant Jamie Lynn Spears will wed fiance CASEY ALDRIDGE at her big sister BRITNEY's Serenity estate in the family's native Louisiana. The teenager 'confirmed' reports she and Aldridge, the father of her baby, had become engaged by wearing a T-shirt sporting the words 'The Rumors Are True' a day after reports surfaced last week (ends28Mar08). And the couple has already set its wedding site, according to OK! magazine. The publication reports the wedding will take place at Britney's country estate - and the pop superstar is expected to be among her sister's bridesmaids. But teenage Spears won't be rushing down the aisle - she's hoping to become an unmarried mum first. A source says, "I expect she'll want to wait at least several months to get her figure back so she can wear a beautiful wedding gown and then have her dream wedding."