Now that Britney's sister Jamie Lynn Spears has just "had the damn Caesarian already," you might think the 17-year-old would be free to raise her new baby in relative peace. Sadly, the newest issue of InTouch arrives bearing the gift of postpartum depression; the magazine has alleged that babydaddy Casey Aldridge has been cheating on Jamie Lynn with an older woman, 28-year-old Kelli Dawson. They even have proof: incriminating pictures of the two touching tongues as though they were eight-year-olds who wanted to try out the exotic concept known as "french kissing." Says the mag:

For months, rumours have circulated that Casey Aldridge has cheated on Jamie Lynn -- but no one has come forward to confirm them, until now. In an exclusive interview with In Touch, 28-year-old Kelli Dawson reveals that she and Casey, 19, were romantically involved -- and were still sleeping together when Jamie Lynn, now 17, was six months pregnant with his child.

The pair didn't bother to hide their relationship. "Kelli and Casey have been a couple on and off for a few years," confirms Jason Alexander, Britney Spears' first husband and a native of nearby Kentwood, La. "They were a really tight couple, but I think it was hard for Kelli, having Jamie Lynn in the picture."

Britney's first, daylong husband? Now that's sourcing! In the face of this incontrovertible evidence, Jamie Lynn would be well advised to take a page from her mother's Guide to Fucking Up Your Children (specifically, Page 119): "Now that the first potential husband is dispensed with, enjoy a wider pool of adventures that involves paparazzi, backup dancers, and Cheeto-covered, high-thread-count sheets."

• Jamie Lynn Spears is betrayed [InTouch]

Tags: britney spears | casey aldridge | hygiene | jamie lynn spears | lynne spears