Local paper the Arizona Republic calls it "brutal, but not unexpected". Mr Gosar made headlines after the violent neo-Nazi rally in Charlottesville, Virginia, in August 2017, by suggesting it was planned by "the Left" to undermine Donald Trump. He then branded Democratic Party donor George Soros a Nazi collaborator in an interview with Vice News.
Horrified, seven of his siblings signed an open letter to the Kingman Daily Miner, stating: "It is extremely upsetting to have to call you out on this, Paul, but you've forced our hand with your deceit and anti-Semitic dog whistle."
Paul Gosar's other controversies include boycotting a 2015 speech to Congress by Pope Francis. He criticised the pontiff's support for climate change, calling it "questionable science" deployed "to guilt people into leftist policies".
He has also defended British far-right activist Tommy Robinson, and attacked "disgusting and depraved" Muslim immigrants at a speech in London in July.
Further anti-Gosar adverts set to air on TV soon include one titled "A family defends its honor," where David Gosar says: "We've got to stand up for our good name, this is not who we are."
"It would be difficult to see my brother as anything but a racist," Grace Gosar says in another, according to the Phoenix New Times.
The Republican, who won his district with 71% of the vote in 2016, is still considered likely to keep the seat he has held since 2011.
If there is a bright side for Mr Gosar, it's that he is one of 10 siblings. While seven have denounced him in public, two are keeping their silence so far - which might make Christmas fractionally less awkward.
His mother has also vocally supported his leadership and politics, leading him to quip: "I guess I really am Mom's favourite"
https://www.bbc.com/news/world-us-canada-45611403
