Britney Spears is sharing a piece of her past.

In her upcoming memoir, The Woman in Me, the Grammy winner accuses her ex-boyfriend Justin Timberlake of cheating on her during their relationship, which spanned from the late '90s into the early aughts. According to TMZ, Spears doesn't name the other woman in her book, though the outlet describes the person as "another celebrity."

Spears' memoir will also include details about the singer getting an abortion after conceiving a baby with Timberlake during their relationship, E! News previously learned.

"Justin definitely wasn't happy about the pregnancy," a passage from the book, published by People Oct. 17, alleges. "He said we weren't ready to have a baby in our lives, that we were way too young."

E! News has reached out to reps for Timberlake, who has yet to publicly address Spears' memoir allegations.

Spears, 41, and Timberlake, 42, who first met while working on The Mickey Mouse Club in the early '90s, officially called it quits on their romance in 2002. Later that year, Timberlake dropped his hit song "Cry Me a River," believed to be about the demise of their relationship, along with a music video that featured a Spears look-alike.

Years later, in Feb. 2021, Timberlake issued an apology to Spears, as well as Janet Jackson, for his past mistakes.

"I've seen the messages, tags, comments and concerns and I want to respond," he wrote on Instagram amid renewed criticism over his handling of his relationship with Spears and his controversial Super Bowl halftime show with Jackson. "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."

"I specifically want to apologize to Britney Spears and Janet Jackson both individually, because I care for and respect these women and I know I failed," Timberlake, who wed actress Jessica Biel in 2012, continued. "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."

The Woman in Me is set for release Oct. 24.

To look back on Spears and Timberlake's relationship over the years, keep reading...

Spears and Timberlake dated between 1999 and 2002 and remain one of the most celebrated famous former couples. Here they are posing in what would become one of the most iconic couple styles of all time at the 2001 American Music Awards.

The two appear attend Clive Davis' annual pre-Grammy Awards party at the Beverly Hills Hotel in 2002.

The two host a Super Bowl fundraiser at the Planet Hollywood restaurant in Times Square in NYC in 2002.

Timberlake joined Spears at the release party for her album Britney in 2001.

The following year, he was her plus one at the premiere of her movie.

Spears was along for the ride when N*SYNC participated at a celebrity basketball game. 

All eyes were on them at music's biggest night.

A very young Spears and Timberlake appeared with All New Mickey Mouse Club co-stars such as Ryan Gosling and Christina Aguilera.