Sen. Lindsey Graham said that former Vice President Joe Biden and his son Hunter have escaped scrutiny so far but should be "looked at" for the pair’s relationship with Ukraine.

The South Carolina Republican told reporters in the Capitol on Thursday that a double standard has allowed the Bidens to skate by without explaining Hunter Biden’s activities on the board of a Ukrainian energy company while his father led U.S. diplomatic relations with the country.

"As to the Bidens, I can promise you no one has looked at whether or not there was a conflict of interest, and no one has taken the time to explain how Hunter Biden got rich in the Ukraine and his father didn’t know anything about it," Graham said. "As much as I like Joe Biden, if it were Lindsey Graham or Mike Pence or Donald Trump, you would be looking."

Graham defended 77-year-old Joe Biden, who is running for the Democratic nomination for president. The lawmaker said that Biden is "one of the finest men I know" but that he needs to explain how his son landed a position on Burisma Holdings’s board with little prior experience in business, particularly the energy sector.

"I don’t think Joe Biden is corrupt, but I don’t think he is beyond being looked at," Graham, 64, said. "I love Joe Biden, but I can tell you I am not going to sit on the sidelines and just watch the Trumps be looked at."

[Also read: Hunter Biden renting $12,000-per-month Hollywood home while refusing to pay child support]

Hunter Biden, 49, has admitted to decades of drug use and was discharged from the Navy in 2014 after testing positive for cocaine. He has been in and out of rehabilitative programs to try to curb his addiction.

The younger Biden is now entangled in a paternity lawsuit with an Arkansas woman, Lunden Roberts, who used to work as a stripper in Washington. Roberts has alleged that Biden is the father to her infant. A paternity test backed up her allegation.

Independence County Circuit Judge Holly Meyer, who is presiding over the custody suit, sent a letter to Biden on Monday, ordering him to show up in court.