Donald Trump, Jr. has slammed Jeopardy! champion Ken Jennings for poking fun at his little brother Barron Trump.

The former game show contestant took to Twitter and responded to reports President Trump's 11-year-old son thought the fake severed head Kathy Griffin was holding in the horrifying photo was really his father.

The 43-year-old wrote on Wednesday: 'Barron Trump saw a very long necktie on a heap of expired deli meat in a dumpster. He thought it was his dad & his little heart is breaking.'

Barron's older brother Don Jr quickly responded, saying: 'It takes a real man to pick on an 11 year old.

'Yet another low from the left, but they will rationalize this away with their usual excuses.'

Donald Trump, Jr. (left) has slammed Jeopardy! champion Ken Jennings for poking fun at his little Barron Trump. It followed reports the president's youngest son thought the fake severed head Kathy Griffin was holding in the horrifying photo was really his father

The former game show contestant, who is now an author, posted this shocking tweet about the president's youngest son, and sparked a furious backlash

Trump said sarcastically that it 'takes a real man' to poke fun at Barron, who is 11

Jennings refused to apologize for his tweet.

In response he posted: 'I will kill as many white rhinos as it takes to prove my masculinity to Donald Trump Jr.'

Jennings is famous for holding the longest winning street on Jeopardy! in 2004.

He won 74 games in a row before he was defeated. His total earnings were $3,196,300.

He now writes a line of educational books for children called Junior Genius Guides.

Some people online have started a campaign to get his publisher, Simon & Schuster, to drop him.

Griffin caused an uproar Monday when she posted a photo showing her dangling a fake head that looked like a bloody, decapitated Donald Trump.

Donald Trump, Jr. has been active on Twitter denouncing the stunt.

In his first tweet, he wrote: 'Disgusting but not surprising. This is the left today. They consider this acceptable. Imagine a conservative did this to Obama as POTUS? '

He then called on CNN to fire Griffin from their New Year's Eve coverage.

Jennings is famous for holding the longest winning street on Jeopardy! in 2004. He won 74 games in a row before he was defeated. His total earnings were $3,196,300

Griffin mocked Donald Trump by holding up a fake bloody severed head that resembled him

President Donald Trump's 11-year-old son Barron was reportedly terrified when he saw a photo on TV and initially believed it was his father

Doubling down: Jennings refused to apologize for his original tweet, instead saying 'I will kill as many white rhinos as it takes to prove my masculinity to Donald Trump Jr.'

The controversial comedian tweeted 'I am sorry. I went too far. I was wrong' after the stunt

Jennings authors a series of educational books called 'Junior Genius Guides' - some are already calling for him to be dropped from Simon & Schuster

He wrote: 'Will CNN keep putting her on air for things like the New Years celebration???'

On Wednesday, CNN fired Griffin from its annual New Year's Eve countdown and she lost several endorsement deals.

She has since apologized, saying: 'I crossed the line.'

Even her longtime New Year's Eve co-host Anderson Cooper condemned the photo.

Cooper wrote: 'For the record, I am appalled by the photo shoot Kathy Griffin took part in. It is clearly disgusting and completely inappropriate.'

On Tuesday, President Trump said his youngest child had been negatively affected by the photo.

'Kathy Griffin should be ashamed of herself. My children, especially my 11 year old son, Barron, are having a hard time with this. Sick!' he wrote on Twitter.

Soon, TMZ published an item with a source saying that Barron had been watching TV when he caught sight of the severed head image.

TMZ said it was told that Barron thought the image was really his father and cried out 'Mommy! Mommy!'

President Trump weighed in Wednesday morning on Kathy Griffin's photo – and he pronounced it 'sick'

'He's 11. He doesn't know who Kathy Griffin is and the head she was holding resembled his dad,' the source told the outlet.

Jennings did not seem at all cowed by Donald Trump, Jr's response, hitting back with 'I will kill as many white rhinos as it takes to prove my masculinity to Donald Trump Jr.'

Trump is known for his big game hunts in which he's been seen posing over the carcasses of dead wild animals.