Angel Carter and Lance Bass to Hold 'Songs for Tomorrow' Charity Concert to Honor the Late Aaron

Chelsea Lauren/WireImage; Gabe Ginsberg/Getty; Paul Archuleta/Getty Angel Carter, Lance Bass and Aaron Carter

Angel Carter and Lance Bass are teaming up to honor her twin brother and late pop star Aaron Carter.

On Wednesday, in honor of her 35th birthday, Angel shared a lengthy message on Instagram detailing why Aaron's death was "the worst day of my life" — and how she plans to take action.

"I want to start by sharing how much I appreciate all the birthday wishes. While today is incredibly tough, I am overwhelmed by your love and support… thank you from the bottom of my heart," Angel began in her post, alongside a photo of herself and Aaron as kids.

"Almost 11 years ago, I lost my sister, Leslie. I remember feeling broken, confused, and I questioned how I was going to continue on without her in my life… And now, over a decade later, I am forced to once again deal with the extreme grief of the death of a sibling," she added. "This time, it's my beloved twin, Aaron. We had an indescribable bond… and now… he is gone."

RELATED: Nick Carter Says It Was 'Tough to Get Up on Stage' with Backstreet Boys After Brother Aaron's Death

"It feels unfair… I feel too young to carry the weight of losing two of my siblings. When we lost Leslie, I was blindsided and shocked. With Aaron, however, we had tried everything. In fact, I spoke with him two days before he passed, and I begged, once again, for him to let us help. I did not know that would be the last time that I would ever hear his voice. And now, I sit here on our birthday, trying to navigate this unimaginable loss because of untreated mental illness and the addiction that it led to."

"Aaron dying was the worst day of my life. I have loved him since we were born… it feels like a piece of my soul is gone. And yet, despite all this pain, his passing has lit a fire within me. I feel a calling and responsibility to help other families and continue the conversation to further break the stigmas that surround mental illness," she added, before detailing the benefit concert happening in Aaron's honor and in effort to "raise awareness about mental health."

The "Songs for Tomorrow" charity concert will take place on Jan. 18, 2023 at Bass' nightclub HEART in West Hollywood, California.

From the concert, 100% of proceeds will be donated to On Our Sleeves, an organization that aims to break stigmas around children's mental health.

She concluded in her post, "I have learned the pain never goes away and keep telling myself that it is one step at a time. I am hoping you can join me for this crucial next step… in memory of Aaron."

The concert will be hosted by Angel and Bass, 43, with special performances by brother Nick Carter, his band the Backstreet Boys, members of *NSYNC, members of O-Town and LFO, Ryan Cabrera, B. Howard and more special guests to be announced.

For more information on tickets and donations go here.

RELATED VIDEO: Aaron Carter, 'LØVË' Artist and Former Child Star, Dead at 34

Aaron died on Nov. 5 at the age of 34. The singer-actor rose to fame in 1997 with his self-titled debut album, followed by Aaron's Party (Come Get It) (2000), Oh Aaron (2001), Another Earthquake! (2002) and LØVË(2018).

Following his death, Nick and Angel also teamed up to launch a donation fund for the same organization, On Our Sleeves.

"Very grateful for the outpouring of love and support for my brother," the Backstreet Boys member wrote in part on his Instagram Story about the fund's creation.

Fans and supporters can make a monetary donation on the fund's page, which features the message, "Thank you for choosing to celebrate the impact of the life of Aaron Carter with a gift of hope. By honoring Aaron, you help Nick, Angel, and their family's commitment of helping others."