Tucker Carlson’s son has bounced from J.D. Vance’s office ... but his decision had nothing to do with the fiery feud between President Donald Trump and his dad.

A source with direct knowledge tells TMZ ... Buckley Carlson is out as deputy press secretary in the VP’s office ... a call he made after an "intense" year in the role. We're told it's common for people to depart the WH after a year ... and this has nothing whatsoever to do with Trump and his pop's bad blood.

Obviously, the timing set off a lot of speculation ... since Trump has been going scorched-earth on Tucker lately -- calling him “low IQ,” “overrated,” and even a “broken man” in recent Truth Social posts -- while Tucker’s been firing back over everything from Iran policy to Trump’s rhetoric, accusing him of crossing serious lines.

Tucker reportedly tried to personally talk Trump out of striking Iran and has since become one of his loudest conservative critics on the issue -- turning their once-friendly relationship into a full-on public slugfest.

But again ... we heard from our source that Buckley made a professionally-based decision-- not a personal one ... as his dad and Trump continue to lock horns in the headlines.