Phillip Faraone/FilmMagic; John Shearer/WireImage
On Friday, Britney's 41st birthday, the singer-songwriter gave a special shout-out to her younger sister, 31, whom she had been publicly feuding with following the end of her 13-year conservatorship.
Alongside two photos of Jamie Lynn, the "...Baby One More Time" singer wrote in the caption, "It's my b-day but you're my heart so I'm thinking about you."
She added, "Congratulations on being so brave, inspiring, and showing guts and glory in your show 🎉 !!! You ain't alone … if anybody knows what that feels like … I get it 🤧🤧🤧 My baby sister !!! I love you !!!"
Britney's dedication to her sister came as a surprise to fans and followers. Earlier this year, Britney's lawyer, Mathew Rosengart, sent a cease-and-desist letter to Jamie Lynn demanding that she stop sharing stories about his client's life while promoting her memoir, Things I Should Have Said.
In response, Jamie Lynn's lawyer Bryan Freedmanfired fired back at Rosengart in a letter of his own, calling out the "vile statements" Britney posted to social media about her sister amid their feud, TMZ previously reported.
Jamie Lynn and Britney had been publicly sparring on social media, with the sisters clashing over claims in Jamie Lynn's memoir.
Britney accused her younger sister of trying to "sell a book at [her] expense" after Jamie Lynn shared stories of her childhood in interviews, including claims that Britney behaved "erratically" at times and once locked the two of them in a room with a knife.
In January, Jamie Lynn shared a message on Instagram insisting that she "is always here" for her older sister while explaining the accusations Britney posts on social media "don't match" what is said between the sisters in private.
"Brit, I am always here for you, you know behind the scenes I have always been here. It's become exhausting when conversations, and texts we have in private don't match what you post on social media," Jamie Lynn wrote, in part.
The "Gimme More" singer also marked her birthday with a photo of her and Sam Asghari that was captured during their wedding day.
In the snap, Spears and Asghari shared a kiss while standing in front of a flower wall. "The man I married 😍 !!! I'm so blessed !!!" Spears wrote alongside the picture.
Asghari, 28, also gave fans a peek into Spears' birthday celebration, sharing a video of cakes, pies, and brownies on display at famed Los Angeles bakery Sweet Lady Jane.
John Mayer's "Love on the Weekend" played over the clip as Asghari thanked the bakery.
It's been a big year for Spears, who made her long-awaited return to music in August. She teamed up with Elton John for "Hold Me Closer." It combines John's "Tiny Dancer" and "The One" with fresh, dance-pop production — and marked Spears' first release since the end of her conservatorship.
RELATED VIDEO: Sam Asghari Opens Up About His Marriage to Britney Spears: 'The Husband Thing Hasn't Hit Me'
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Spears posted on her Twitter account and shared her excitement with fans about the song and where she was in life.
She wrote in part, "Okie dokie … my first song in 6 years 🎶 !!!! It's pretty damn cool that I'm singing with one of the most classic men of our time … @eltonofficial 🚀!!!! I'm kinda overwhelmed… it's a big deal to me !!! I'm meditating more 🧘🏼♀️ and learning my space is valuable and precious !!!"
She continued, "I'm learning everyday is a clean slate to try and be a better person and do what makes me happy … yes I choose happiness today. I tell myself every day to let go of the hurt bitterness and try to forgive myself and others to what may have been hurtful. I want to be fearless like when I was younger and not be so scared and fearful. I pray there actually is truth to the Holy Spirit and I hope that spirit is with my children as well !!! Yes … I choose happiness and joy today ☀️ !!!?"