Britney Spears' younger sister, Jamie Lynn Spears, is opening up about their family feud for the first time.

Jamie Lynn, 30, appeared on "Good Morning America" on Wednesday to discuss the upcoming release of her new memoir and to share her side of the story in the ongoing plight between her pop star sister and the rest of her family.

Growing up, Jamie Lynn says she "adored" Britney and thought of her as "another mama." But over the years she witnessed the "Toxic" singer's behavior become "erratic, paranoid, spiraling," she writes in the book, according to the interview.

Jamie Lynn declined to comment on what she thinks of Britney's current state of mind, as "that's not fair."  "But I'm allowed to say how I felt in those because that matters. It matters that I was in pain."

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Jamie Lynn Spears, 30, appeared on "Good Morning America" on Wednesday to discuss the upcoming release of her new memoir. (Image Group LA/Disney Channel via Getty Images)

The "Toxic" singer was first placed under a conservatorship in 2008. Jamie Lynn recalls being "happy" when the conservatorship was dissolved for good last fall. 

"I was happy," she said, adding that she still doesn't understand what the conservatorship was all about. "I was about to have a baby so I didn't understand what was happening nor was I focused on that. I was focused on the fact that I was a 17-year-old about to have a baby. I understand just as little about it then as I do now."

In her upcoming book, Jamie Lynn discusses being asked to play a role in the conservatorship by her big sister.

"There was a time when my sister asked me off her trust and will if I would be the person that ensured her boys got what they needed. Whether she's in a conservatorship or not, that was a very normal thing I thought. Once I realized you know what she's in a conservatorship, I just didn't want to be a part of until maybe she was out of the conservatorship. There was no me overseeing funds and if that was that was a misunderstanding. Either way, I took no steps to be a part of it," she said.

Jamie Lynn went on to claim that she tried to step in and help her sister amid her conservatorship struggles. 

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Britney Spears Jamie Lynn Spears

Britney has since called out her family, including Jamie Lynn, for profiting off of her fame and fortune. (Image Group LA/Disney Channel via Getty Images)

"If she wanted to talk to other people then I did. I set that up. I even spoke to her previous legal team and that did not end well in my favor. I did take the steps to help. But how many times can I take the steps without, you know, she has to walk through the door," Jamie Lynn added.

Britney has since called out her family, including Jamie Lynn, for profiting off of her fame and fortune. While the siblings' discord has played out in the public eye, Jamie Lynn was brought to tears when sharing how she truly feels about their relationship.

"That love is still there 100%. I love my sister. I've only ever loved and supported her and done what's right by her and she knows that so I don't know why we're in this position right now," she said amid tears.

Jamie added that she believes she "cleared up" the issue Britney took over Jamie Lynn's performance at the 2017 Radio Disney Awards, where she performed a remix of her older sister's songs. "I don't like that my sister showed up at an awards show and performed MY SONGS to remixes !!!!!" Britney wrote in a post that was also critical of her father, Jamie, who controlled her conservatorship at the time. 

Also in her memoir, "Things I Should Have Said," Jamie Lynn details growing up around her father, James P. Spears', alcoholism. According to court documents obtained by the New York Times, James P. Spears, also known as Jamie Spears, attended rehab for alcoholism 2014, when Jamie Lynn was a teenager. In the book, Jamie Lynn writes, "He spent most of my life in that cycle of ruinous behavior. His bouts of drinking always causing periods of torment and sorrow."

Jamie Lynn told ABC"s Juju Chang that her father's drinking "created a lot of anxiety" for her. "The hardest part was like, could I trust you? Are you drinking? Are you not? It was something that no kid should have to question," she said.

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Jamie Lynn Spears

In her upcoming book, Jamie Lynn discusses being asked to play a role in the conservatorship by her big sister. (John Shearer/WireImage)

As for why Jamie Lynn decided to go ahead and write her memoir, she said, "It was really important for me to, first off, honor my voice. I have to do it or how else can I expect my daughters to stand up for themselves?"

Britney and her father did not immediately return Fox News' request for comment. 

Jamie Lynn's tell-all memoir is set to be released on Jan. 18. 

Britney and Jamie Lynn's strained relationship became public in the past year as the "Toxic" singer sought to free herself from her conservatorship. In Britney's legal fight, the pop star called out her family members both in court and on social media for failing to help free her from the 13-year court order. Specifically, Britney accused her and Jamie Lynn's father, James P. Spears, of "conservatorship abuse." She also claimed her family has profited off of her fortune.

Britney kicked off 2022 by purging a lot of her followers on Instagram, including her famous sister.  The move marks the latest passive-aggressive move from Britney regarding both her sister and the rest of her family, who she has blamed publicly on multiple occasions for keeping her under the harmful legal deal until a judge finally terminated it in November.

Jamie Lynn’s involvement with the conservatorship came to light in 2019. It was revealed that Jamie Lynn was named as the trustee in Britney’s SJB Revocable Trust in 2020, which was amended by Britney’s then-co-conservators in 2018, according to legal documents.

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Britney Spears's family from l-r: Jamie Spears, Bryan Spears, Jamie-Lynn Spears, Britney Spears and Lynne Spears. (Kevin Mazur/WireImage)

When Britney made her explosive 2021 court appearance and publicly called for her freedom from the deal for the first time, she also called out her family without naming her sister directly. She also laid out shocking allegations, like being forced to work long hours, being denied the right to remove her IUD and being completely removed from handling her own finances.

Days later, Jamie Lynn released a statement after receiving backlash for not publicly supporting the #FreeBritney movement, which sought to end her sister’s conservatorship long before her 24-minute court testimony. In a video posted to her Instagram Stories, Jamie Lynn said that she stayed quiet about the situation because she believed her sister could speak for herself. 

"Since the day I was born, I've only loved adored and supported my sister. I mean this is my freaking big sister, before any of this bulls-. I don't care if she wants to run away to a rainforest and have zillion babies in the middle of nowhere, or if she wants to come back and dominate the world the way she has done so many times before, because I have nothing to gain or lose either way," she said at the time. "This situation does not affect me either way, because I'm only her sister who's only concerned about her happiness."

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At one point, Jamie Lynn noted that she was previously getting death threats. However, that all changed in October when the former Nickelodeon star announced that she was releasing "Things I Should Have Said." Due out later this month, the book promises to discuss things like her sister’s conservatorship, her first pregnancy when she was 16 and her daughter’s near-fatal ATV accident in 2017. 

Fox News' Tyler McCarthy contributed to this report.