The pair, who turned 43 on October 21, took a sweet selfie to mark the occasion.
"Birthday twinning.. spent all my years around the sun with this guy! Pretty awesome," Stewart wrote.
"Happy birthday (for yesterday) bro."
This is not the first time Stewart has taken to Instagram to share an epic picture of his twin brother!
Sharing a sweet selfie of the two earlier this year, James wrote: "Same same, but different", adding the hashtags "Family" and "Twins".
James rarely shares snaps of his identical twin brother Nicholas, so unsurprisingly fans were shocked.
Many took to the images comment section to share their amazement.
One wrote, "OMG 😮", with another adding, "You're a twin? Never knew that".
Another eager follower echoed, "I got so confused I just woke up and actually typing with one eye open so this really confused me 😂😂😂😂"
Happy Birthday to the Stewart brothers!
This article first appeared on New Idea.