Britney Spears' sis gets pregnant

Jamie Lynn Spears, the 16-year-old “Zoey 101” star and sister of Britney, tells OK! Magazine that she’s pregnant and that the father is her longtime boyfriend, Casey Aldridge.

“It was a shock for both of us, so unexpected,” she says. “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.

“As soon as I found out for sure from the doctor, I took two weeks to myself where I didn’t tell anybody,” she says. “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.”

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

“She was very upset because it wasn’t what she expected at all,” Spears says. “A week after, she had time to cope with it and became very supportive.”

Lynne Spears, already grandmother to Britney’s young sons, says: “I didn’t believe it because Jamie Lynn’s always been so conscientious. She’s never late for her curfew. I was in shock. I mean, this is my 16-year-old baby.”

She says her actress daughter, the telegenic heroine of the popular Nickelodeon series “Zoey 101,” has known Aldridge for years and began dating him in high school.

One person who might not be so thrilled by the news? Britney. A source close to the pop princess told TMZ.com that Jamie Lynn’s older sister is “frantic” over the news. The Web site reports that Britney may not have been aware of the news until today.

Jamie Lynn plans to raise the baby in her home state of Louisiana — “so it can have a normal family life.”

The third season of “Zoey 101” wraps up Jan. 4.

“I haven’t spoken to (Nickelodeon) personally, but they have always been so great to me over the past years and have given me so many opportunities.”

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 says. “But I can’t be judgmental because it’s a position I put myself in.”