Derick Dillard is accusing Jim Bob Duggar of being deceitful and manipulative.
Derick wrote, "I used to have much respect for Jim Bob, as my father-in-law, and I wanted to give him the benefit of the doubt for years. Unfortunately, it's only become clearer to us over time just how deep this man's manipulation and deceit will go for his own gain, at the expense of others."
According to Derick, Jim Bob has lied to him and Jill "numerous times."
"When confronted privately, he is not humble, but he is defensive and verbally abusive," Derick continued. "When he says he cannot be bought, the truth is that he has a history of being a sellout to anything that he can personally profit from, and he will justify it however he wants to continue his personal agenda."
Derick added, "Again, if he has lied and continues to lie to his best friends and his own family, will he LIE to YOU?!"
E! News reached out to Jim Bob for comment.
Jill and Derick left the family's spin-off show Counting On in 2017 and have since distanced themselves from the Duggars, saying their "control" over some aspects of their lives was "taken away."
Derick's comments are on the latest to come from members of the Duggar family in recent days, after eldest son Josh Duggar, 33, was convicted of receiving and possessing child pornography last week.
Jill and Derick previously addressed Josh's conviction in a statement shared to their website on Dec. 9. They wrote, "Today was difficult for our family. Our hearts go out to the victims of child abuse or any kind of exploitation."
"Josh's actions have rippled far beyond the epicenter of the offense itself," continued the Dillards. "Children have scars, but his family is also suffering the fallout of his actions."
Jim Bob and wife Michelle Duggar also expressed sympathy to victims of sexual abuse, telling E! News in a statement, "This entire ordeal has been very grievous. Today, God's grace, through the love and prayers of so many, has sustained us. Our hearts and prayers are with anyone who has ever been harmed through CSAM [Child Sexual Abuse Material]."
Josh is currently in custody and awaiting his sentencing. He faces up to 20 years in prison for each count, and fines of up to $250,000 for each count. His attorneys said in a statement to E! News, "We appreciate the jury's lengthy deliberations... We respect the jury's verdict, and we intend to appeal."