According to the pop star, she practically raised her younger sister. Britney wished Jamie a happy belated birthday on Friday, April 9, saying on Instagram, "It's weird to say that I was basically your momma when you were younger and yes I'm still older but your soul is and always has been wise !!!!"
She called the Zoey 101 star a "beautiful soul," writing, "I love you so much and damn it I wish I was as smart as you at 30 !!!!"
Britney, 39, gushed, "I'm truly and genuinely inspired by your path and the life you have created for your beautiful children and I'm so f--king proud to call someone as beautiful inside as you my sister !!!!"
She said she's always been shocked by Jamie Lynn's physical strength. Britney recalled a moment "I'll never forget" when the "classy Southern chicks" decided to play wrestle at home—"and you put me to the floor in literally two seconds after I gave all my might."
The "Piece of Me" singer wrote, "You're so DAMN STRONG ... I was extremely taken back and still am to this very day !!!"
Though you might think their wrestling match was a memory from their childhood, it seems it only happened a few years ago. According to Britney, "Maybe we should have a rematch ... I mean things have changed since 6 years ago !!!!!" Maybe she can tag-team with her fitness-focused boyfriend, Sam Asghari.
Britney ended her birthday note by reiterating, "I wish I was as strong as you," which some fans speculated was a reference to Britney's longtime battle against their father, Jamie Spears, over control of her career and estate.
Other fans, meanwhile, were more flabbergasted by the picture Brit chose to accompany the cryptic birthday message. The throwback pic showed little Jamie Lynn with her glasses on, sitting next to Britney and her ex-boyfriend, Justin Timberlake.
The timing was odd, considering the renewed interest in their highly-publicized relationship, following The New York Times' recent documentary episode, "Framing Britney Spears."
In fact, Justin released a statement apologizing to both Britney and Janet Jackson in February, amid rising outrage from fans online over the misogynistic culture in 2000s.
"I've seen the messages, tags, comments and concerns and I want to respond," the ‘N Sync alum said. "I am deeply sorry for the time in my life where my actions contributed to the problem, where I spoke out of turn, or did not speak up for what was right. I understand that I fell short in these moments and in many others and benefited from a system that condones misogyny and racism."
Justin "specifically" wanted to say sorry to the two musicians "because I care for and respect these women and I know I failed. I also feel compelled to respond, in part, because everyone involved deserves better and most importantly, because this is a larger conversation that I whole heartedly want to be part of and grow from."
As for that wrestling rematch, it doesn't sound like Jamie Lynn is too interested. The actress responded solely with emojis, including the hatching chick, white heart, twins, infinity sign and praying symbols.