"It runs in the family. I never wanted to tell anyone this. But I have too (sic)…," he wrote.
"My sister Leslie suffered from bipolar and took lithium to treat it. She never liked the way it made her feel and when she was off of it she did things that she never meant to do I truly believe that. I was 10 years old…."
"My sister raped me from the age of 10 to 13 years old when she wasn't on her medications and I was absused (sic) not only sexually by her but by my first two back-up dancers when I was 8 years old. And my brother absused (sic) me my whole life."
Leslie died in 2012 from a drug overdose when she was 25-years-old.
The singer handed over two assault rifles on Wednesday after his brother Nick Carter reportedly took out a restraining order against him.
He says he has kept his shotgun and pistol for his own protection.
Aaron Carter has made a series of troubling statements about his family on Twitter recently, including accusing his brother Nick of being a "serial rapist" and accusing his pregnant sister of being on drugs.
The Backstreet Boys singer Nick, 39, said he filed the order against his brother after he expressed the intention of killing Nick's pregnant wife, Lauren Kitt, and their unborn child.
"In light of Aaron's increasingly alarming behaviour and his recent confession that he harbours thoughts and intentions of killing my pregnant wife and unborn child, we were left with no choice but to take every measure possible to protect ourselves and our family," Nick tweeted this week.
"We love our brother and truly hope he gets the proper treatment he needs before any harm comes to himself or anyone else."
