"It would be hard to see my brother as anything but a racist", Mr Gosar's sister Grace tells voters in another upcoming advert, according to The Phoenix New Times.
"Paul's absolutely not working for his district", says "David, lawyer". "I bet he'd be researching what is the most insightful water policy to help the environment in Arizona sustain itself and be successful".
"He's not listening to you, and he doesn't have your interests at heart", pipes in a private investigator named "Tim".
Brill's ads, of which there are at least three, were filmed in Jackson and Laramie, Wyoming.
The clips of passionate Arizonians slamming Congressman Paul Gosar seem like pretty standard attack-ad fare-until the 0:42 mark when Tim says "My name is Tim Gosar", followed by the other speakers revealing their full names: David Gosar, Grace Gosar and Jennifer Gosar.
He also called Democratic Party donor George Soros a Nazi collaborator in an interview with another news outlet.
"There's no dispute about our opposition to him", Gosar said.
Paul Gosar's comments about Soros came in a television interview with Vice News in which he also suggested a 2017 white supremacist rally in Charlottesville, Virginia, might have been a liberal conspiracy.
Every family has their political differences. but this is on another level. Earlier this year, he called for authorities to check the immigration status of those attending the State of the Union address, and arresting and deporting "any illegal aliens attempting to go through security".
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 think my brother has traded a lot of the values we had at our kitchen table".
Gosar, a four-term incumbent running for re-election in northeastern Arizona, is a vociferous supporter of President Trump and a conservative hardliner.
The six who spoke out are not the Congressman's only siblings.
So is this a shock move from David, Tim, Jennifer, Gaston, Joan, and Grace? She said she supported her son's beliefs. Then he wrote, "You can't pick your family". The counties that make up Gosar's district voted heavily for US President Donald Trump.
It's hard to get six siblings to agree on anything.
He faces an uphill battle for the seat; Gosar trounced his Democratic opponent in the deep-red district in 2016, receiving 71.5 per cent of the votes.