"The two Biden brothers have long held a commitment to pushing environmental issues to the forefront," part of the ad for the South Florida-based Berman Law Group said, according to CNBC.
The ad, printed in Florida’s Daily Business Review, featured a picture of Frank Biden and focused on the firm’s lawsuit against a group of sugar cane companies in Florida, according to CNBC.
"My brother is a model for how to go about doing this work," the president's brother reportedly said in the ad.
Frank Biden is listed on the company’s website as a non-attorney senior adviser and his short biography also notes his relationship with his brother.
"Mr. Biden worked in the Clinton Administration as a Director of Legislative and Congressional Affairs and was involved in the election campaigns of his brother, Joe Biden, and nephew, Joseph R. Biden III, as an advisor and unpaid campaign coordinator over many years," it says on the website.
Frank Biden told CNBC in an email that he has never used his brother to get new clients. "Our firm has long been involved [with] this lawsuit," he wrote. "Social justice is something I have been involved in for years. I will never be employed by any lobbyist or lobbying firm."
Matthew Moore, an attorney with Berman Law Group, told CNBC that Frank Biden has been with the firm for years and is a "champion for social justice, advocating against corporate behemoths that prey on the little guy.
He continued, "The big sugar case has been around for more than 2 years and is the poster child for corporate influence. We are honored to have Frank Biden stand with us as leaders for social justice."
The firm did not answer a Fox News after-hours' call for comment.
A White House spokesperson told CNBC it is the administration’s policy "that the President’s name should not be used in connection with any commercial activities to suggest, or in any way that could reasonably understood to imply, his endorsement or support."
A White House representative did not immediately respond to Fox News' after-hours' request for comment.
Frank Biden has used his connection to his famous brother for other business dealings as well, according to an ABC News story last year and once referred to his last name as "a tremendous asset."
President Biden’s son Hunter Biden has also faced questions over his position on the board of a Ukrainian oil company while his father was vice president and other business dealings in China.
While neither Biden has been charged with any wrongdoing, critics say the moves could create the appearance of impropriety.
"The Biden White House has to have a very strict protocol on the using of the Biden name," former George W. Bush White House ethics lawyer Richard Painter told CNBC. "Brothers, law firm associates and anyone else who is using the Biden name should not be contacting the president or anyone else working with the president."
Former President Trump's adult children have also faced accusations of profiting off their father's presidency for their personal businesses and of nepotism in the White House.