Britney's pregnant baby sister, Jamie Lynn, celebrated the eve of her 17th birthday by hitting up a Louisiana JC Penney on Thursday -- with her soon-to-be baby daddy Casey Aldridge. Awww. What great role models.
The expectant parents are allegedly engaged. They're the teen Brangelina!
America's Favorite Unwed Pregnant Teen Turns 17
4/4/2008 2:33 PM PDT BY TMZ STAFF
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