Donald Trump Jr. calls himself his brother's 'hero' in birthday Instagram post

Drew Angerer/Getty Images

Eric Trump and Donald Trump Jr. speak during a ribbon cutting event at Trump Golf Links at Ferry Point in The Bronx.

• President Trump's eldest son, Donald Trump Jr., wished his brother, Eric, a happy birthday with a throwback photo on Instagram.
• The photo's caption is signed, "Your Hero Don."
• This isn't the first time Don Jr. has poked fun of his brother, a fellow executive vice president at The Trump Organization. 
• While other members of the Trump family have yet to wish Eric a happy birthday, his sister, Ivanka, also shared a throwback image.

Donald Trump Jr. doesn't shy away from poking fun at his brother, Eric - even on his birthday.

In celebration of Eric turning 35 on Sunday, the president's eldest son posted a throwback photo of his younger brother in a white jumper with bowl-cut hair and a visible grimace on his face.

Read more: Michael Cohen's plea deal poses a significant danger to Donald Trump Jr.

"Happy birthday to the best little brother in the world," Don Jr. wrote. "People tell me you've grown and such but I'll always remember you just like this pic."

The caption is signed, "Your Hero Don."

The two brothers, who serve as executive vice presidents at The Trump Organization, are often satirized in tandem on Saturday Night Live, with Don. Jr. portrayed as a smooth-talker and Eric as the bumbling second-in-command.

Don Jr. has embraced the parody on Instagram.

On Sunday, Eric also received birthday messages from the GOP and his older sister, Ivanka, who posted a less embarrassing photo on Twitter.

Though both Ivanka and Don Jr. appear to be in good spirits, the Trump children could face a tough year ahead.

Washington insiders speculate that Don Jr. may be indicted over claims that he lied about not telling his father about a meeting with Russian officials, where he promised "dirt" about Hillary Clinton.

Mueller may also intend to question Ivanka, who helped strategize about how to handle the backlash, when the time is right.