Presidential son Donald Trump Jr. continues to stoke his feud with former vice president Joe Biden, this time claiming Joe is so forgetful he shouldn’t be U.S. president.

Don Jr.'s latest attack on Biden came only three days after he blasted Joe for an old "hairy legs" controversy that took place way back in September 2017. On Wednesday, Don Jr. criticized Biden for forgetting which year he was vice president.

This latest Biden gaffe having to do with forgetfulness came at a campaign event in New Hampton, Iowa. Biden was answering a question from someone in the audience when he said, “We (he and former president Barack Obama) did that in 1976... Um, I mean, excuse me, backing up here, 2014 is when we did that.”

Joe did remember to correct himself but that didn't stop Don Jr. from bashing the VP on Twitter anyway.

"Are we really supposed to believe that a guy who can't even remember what year he was Vice President and regularly has trouble remembering where he is at any given moment is capable of leading the free world?  Give me a break," tweeted Don Jr.

His tweet was liked and shared by likeminded conservatives. Some of these people had pretty nasty things to say about Biden, who is now 77 years old and the oldest among all Democrats contending the party's nomination for presidential candidate. One commenter noted Biden was 34 in 1976 while Obama was still in high school.

This event was the same one that made headlines of another kind when Biden called an 83 year-old man "a damn liar, man" for claiming Biden got his son, Hunter, to work with the Ukrainian oil company Burisma. This man also said Biden was too old to be president.

"One, is you're damn near as old as I am," said the man. "You're too old. I'm 83 and I know damn well I don't have the mental faculties I did ... 30 years ago."

As for Hunter, the man said, "So you're selling access to the president, just like (Trump) is."

Those were fighting words and Biden was having none of it.

"You're a damn liar, man," he replied angrily to the Burisma claim. "You said I set up my son to work at an oil company. Isn't that what you said? Get your words straight, Jack!"

As for him being too old to be president, Biden said: “I’m not sedentary,” said Biden. "Look, the reason I’m running is because I’ve been around a long time and I know more than most people know and I can get things done. That’s why I’m running. And you want to check my shape, man, let’s do push-ups together here, man, let’s run, let’s do whatever you want to do, let’s take an IQ test."

An NBC/Wall Street Journal poll last February found 62% of voters either had "reservations" or were "very uncomfortable" voting for a candidate older than 75.

Democratic presidential candidate Joe Biden speaks during the Iowa Democratic Party Liberty & Justice Celebration in Des Moines, Iowa Democratic presidential candidate Joe Biden speaks during the Iowa Democratic Party Liberty & Justice Celebration in Des Moines, Iowa Photo: GETTY IMAGES / Joshua LOTT