In another video, Grace says: "It would be hard to see my brother as anything but a racist".
Gosar's siblings appeared in other ads for Brill that were uploaded to his YouTube page. The siblings - Tim, Jennifer, Gaston, Joan, Grace and David Gosar- say they are making a values-based endorsement of Brill, and that their brother is too extreme in his views. "This is not who we are", David Gosar says. Another said he traded in everything he learned around the family kitchen table.
The Democratic candidate, Dr. David Brill, released the videos, drawing astonishment at the rare public display of a family fighting over political views (although it was not the first time this year) as well as jokes about what a Gosar Thanksgiving gathering might be like.
Gosar is now calling himself "Mom's favorite" because, after six of his brothers and sisters insulted his policies and endorsed his opponent, his mother came forward to say that she will definitely vote for him. Then he wrote, "You can't pick your family".
Dave Gosar, one of the six siblings who appear in the ad attacking Paul Gosar, also has a twitter account that he uses to troll his brother.
"(Gosar) 's not listening to you.
Paul Gosar, a dentist, is the eldest sibling in his family. He promoted the conspiracy theory that the white supremacists' rally in Charlottesville, Virginia, past year was a plot by the left financed by Democratic megadonor George Soros, who Gosar said "turned in his own people to the Nazis".
Rep. Gosar responded Saturday, saying his siblings are just President Trump haters and disgruntled leftists who put politics before family, adding.
Gosar's younger brother, Pete, was a college football player at the University of Wyoming, where the Gosars grew up, and Pete ran for governor in Wyoming twice and was the Democratic nominee in 2014, but eventually lost in the general election. "I'm not going to break bread with a racist". He also said Soros, a Democratic fundraiser, collaborated with Nazis during World War II, a claim pushed by far-right pundit Alex Jones and InfoWars. Once they were described to her in detail, she said she was "shocked" and "crushed".
In addition to the ads, Joan, who lives in Idaho Falls, Idaho, donated $1,000 to Brill's campaign, filings show.
But in the deeply red state, pollsters predict Mr Gosar is still likely to retain his seat - the Congressman won his seat with more than 70 per cent of the vote in 2016. In the video, she and five other siblings urged voters to cast their ballots against their brother in November 2018.