US Weekly says that Lynne Spears told Kevin Federline about Jamie Lynn's pregnancy before she told Britney. Apparently this is no big shocker to people familiar with the situation, one of whom said:
Lynne talks with him way more than she talks to Britney.
Well, it's hard work talking to someone who can barely form coherent words much less put sentences together. Plus we all know Kevin and Lynne are fucking, so it was probably just after-sex talk.
Lynne (puffing a cig): "Did I mention Jamie Lynn is pregnant?"
Kevin: "Damn baby, that's wack. Uh, would you mind climbing on this thing one more time? Popozao needs some more of your hot but so-wrong lovin' baby-grandma."
(source)