We're told Jamie Lynn was extremely nervous before the birth, but our spies tell us big sister Brit "made a big difference" and helped a ton -- giving her advice and support.

JL's bro Brian was on family patrol, calling everyone with the news. As for a name -- the kids didn't narrow it down til the very last second. People says lil' Spears' will be called is Maddie Briann. - more on this story

Preview and Purchase Britney Spears CDs