"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
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...
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??I made a choice to lay low this year to focus on becoming my best self. 2018 has a lot coming, so GET READY.... #12DaysofJLS pic.twitter.com/1Mhj2KgYOl— Jamie Lynn Spears (@jamielynnspears) December 24, 2017
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
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.
Photo Credit: Getty / Image Group LA