"Thank you for your endless sacrifices, your belief in me, you always pointing me to Christ, and the countless memories we've made together," he captioned a photo of his dad holding him when he was a toddler. "I am grateful to call you my dad, and I'm proud to be your child."
"Regardless of what anyone may say, your the best dad in the world!" he continued. "Today, and every day, I celebrate you and the incredible father you are. Love you a Ton!" he concluded, adding the hashtags "#FathersDay" and "#bestdadever."
Followers rushed to the comments to drag the 21-year-old, with one critic replying, "I think you mean Happy Father's Day Jill. Your parents did not raise you," referring to the Duggar family's "buddy system" in which older children were assigned younger children to care for throughout the day to help take some of the workload off of the parents.
Other than James, younger sisters Joy-Anna and Jennifer were also Jill's assigned "buddies."
"This is sad," another user wrote. "Jill basically raised you and yet you support and thank the man who has hurt her time and time again. Shame on you."
But according to an insider, Jill isn't surprised by James' subtle shade. "Boys are valued more than girls," the insider dished to an outlet of the Duggar family's dynamic. "It distresses Jill that her younger siblings are being brainwashed in this toxic environment."
This comes nearly one month after Jill, 32, slammed the Duggar family patriarch in Prime Video's tell-all docuseries Shiny Happy People: Duggar Family Secrets, claiming he hadn't paid her or her husband for their time on the lucrative TLC show for seven and a half years of her adult life.
The mother-of-three — who shares Israel, 7, Samuel, 5, and Freddy, 11 months, with husband Derick — stated in an interview that whenever Jim Bob gave her contract paperwork, it was only the final signature page, so she wasn't able to read the legal agreement in full.
Eventually, Derick and Jill both spoke with Jim Bob about the possibility of getting a paycheck for having their lives play out on screen, but the father-of-19 only offered them $10 per hour, which was just above Arkansas minimum wage at the time of their talk.
Meanwhile, it's been reported the 57-year-old was bringing in anywhere from $25,000 to $45,000 per episode, earning a total of around $850,000 per season by the end of their TLC run.
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"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," Derick said in the documentary.
The source spoke with Star magazine about James' comments.