On September 3, Collin, also 16, accused his father of abuse, writing in a since-deleted post, "My dad is a liar. Yesterday he beat me up and thought nothing of it, he punched me in the face and gave me a swollen nose and I started bleeding. He then continued to kick me in the ribs after I was on the floor. He is a liar."
At the time, Pennsylvania Child & Youth Services looked into the claims, but later released a statement saying, "No charges or citations were filed as a result of that incident. We are not investigating at this point."
And Hannah confirmed to the news outlet that she told police she had witnessed the incident and that Jon did not hit her brother.
"Collin is facing many difficult issues and my dad is doing everything in his power to help him," she explained. "My dad loves us and has never been abusive to us in any way."
"I am done hiding and will say this unequivocally: Jon is a violent and abusive person," she told People.
Although no charges have been brought against Jon, Kate said she believes there is more work to be done with the investigation.
"Until I receive the letter from CYS about whether they've deemed the allegations founded or not, it's ongoing," she claimed. "My contact at CYS has not told me otherwise. If this doesn't qualify as assault, I don't know what does."
A rep for Jon denied all claims in a statement to E! News.
"Jon has never abused Collin," the statement read. "Collin has endured severe trauma. Jon is a loving father who has worked hard to ensure that his son gets the support and help he needs."
Kate and Jon divorced in 2009 after ten years of marriage. They shot to fame in 2007 with their reality show "Jon & Kate Plus 8".
19-year-old twins Cara and Madelyn live with their mother, as do four of the 16-year-old sextuplets Alexis, Aaden, Joel and Leah; while the remaining two siblings — Hannah and Collin — live with their dad.