The 22-year-old 19 Kids and Counting star took to Twitter on Tuesday, where she linked to a blog post written by her father-in-law Michael Seewald condemning Josh for being "a pretender" who sinned against God.
"Go to seewalds.com and read the post on the Ashley Madison scandal," Jessa tweeted, linking back to the family's personal website.
In the strongly worded open letter published Monday, Jessa's father-in-law wrote, "Though I have never gotten to know Josh very well, I have great respect for his sorrowing parents and immense sympathy for his dear wife Anna and their four children."
The post was written in the wake of Josh's admission to infidelity and addiction to pornography after it was revealed that he had signed up for the adult extramarital dating site Ashley Madison.
"It distresses me to say that Josh Duggar’s greatest sin is a byproduct of the sum total of his secretly sinful lifestyle. That is, that by his hypocrisy, he blasphemed the name of God. He claimed to be a Christian, but by his deeds he has suggested otherwise," Michael expressed in the lengthy post, which he says he wrote because of "an overwhelming desire to vindicate the name of God."
Last month Jessa hinted at the scandal surrounding her brother when she Instagrammed a photo of a Bible passage -- specifically 1 John 1:6, which reads, "If we say we have fellowship with [God] while we walk in darkness, we lie and do not practice the truth."
Josh allegedly check himself into a Christian rehab center to seek treatment and recovery, according to a statement written by the Duggar family. Check out the video below to hear more.