COCOA BEACH, Fla. -- The two youngest children in U.S. history to be tried as adults for first-degree murder are scheduled to be released from prison in the next nine days, according to ABC News.

Curtis and Catherine Jones were 12 and 13 years old, respectively, when they pleaded guilty to second-degree murder in the killing of their father's girlfriend, Nicole Speights, in 1999.

The siblings were given an 18-year sentence and will be on probation for the rest of their lives.

WFTV reported that the siblings accused a male relative of sexually abusing them, but their father and his girlfriend ignored their pleas for help. That's when the siblings began plotting to kill all three people involved. They did not go through with their plan after shooting Speights.

Florida Today reported that child services found some signs of abuse, but nothing was ever proven.

Prosecutors told ABC News that the reports of sexual abuse were not dealt with in court.

Curtis is now an ordained minister and Catherine married a pen pal, according to Florida Today.

"Of course there are fears, mainly because there's so much I must learn to function like a normal person: how to drive, fill out job applications, text, dress for a job interview, build my credit," Catherine wrote in a letter to Florida Today in 2014.

Catherine is scheduled to be released Aug. 1 and Curtis is scheduled for release on July 28.