Another Spears baby is reportedly on the way — and it's not Britney's. Jamie Lynn Spears, the 16-year-old "Zoey 101" star and sister of Britney, told OK! magazine that she's pregnant and that the father is her boyfriend, Casey Aldridge.

"It was a shock for both of us, so unexpected," she said. "I was in complete and total shock and so was he."

Spears is 12 weeks along and initially kept the news to herself when she learned of the pregnancy from an at-home test and subsequent doctor visit, she told the celebrity magazine, which hits stands in New York on Wednesday and the rest of the country by Friday.

What message does she want to send to other teens about premarital sex? "I definitely don't think it's something you should do; it's better to wait," she told the magazine. "But I can't be judgmental because it's a position I put myself in."

After she found out from a doctor that she was pregnant, she said, "I took two weeks to myself where I didn't tell anybody."

"Only one of my friends knew because I needed to work out what I would do for myself before I let anyone's opinion affect my decision. Then I told my parents and my friends. I was scared, but I had to do what was right for me," she said.

Spears broke the news to her mother, Lynne, just before Thanksgiving, the magazine reported.

"She was very upset because it wasn't what she expected at all," Spears said. "A week after, she had time to cope with it and became very supportive."