Britney Spears Reacts to Sister Jamie Lynn's Pregnancy

Jamie Lynn Spears announced on Sunday that she is expecting her second child, and sister Britney Spears was one of the first to congratulate the singer on her happy news.

"Maddie is going to be the best big sister!!!" the pop star wrote alongside Jamie Lynn's original announcement. "So happy for you @jamielynnspears!!!! Love you all sooo much!!!"

Jamie Lynn shared the news of her pregnancy on social media Sunday night, posting a photo of herself standing hand-in-hand with husband Jamie Watson and her daughter, Maddie.

"Looks like we are starting off 2018 with another big milestone...sooo happy to announce that Maddie is FINALLY going to be a big sister," she wrote. "I made a choice to lay low this year to focus on becoming my best self. 2018 has a lot coming, so GET READY...."

The 26-year-old shares 9-year-old Maddie with her ex-fiancé, Casey Aldridge.

Jamie Lynn's new addition will have plenty of cousins to play with, as Britney is mom to sons Sean, 12, and Jayden, 11, and brother Bryan is dad to daughter Lexie.

Britney also got into the celebratory spirit recently, sharing a video of her son celebrating a break from school by jumping for joy in front of a decadently decorated house.

Jumping for joy because school is out for the holidays!! 🎄

A post shared by Britney Spears (@britneyspears) on

Photo Credit: Getty / Image Group LA