'Pioneer Woman' Ree Drummond's Nephew, Caleb, Arrested for DUI

'Pioneer Woman' Ree Drummond's nephew, Caleb, was arrested for DUI just over a month after he was involved in a scary wreck that could've claimed his life ... TMZ has learned.

According to arrest records out of Osage County, OK ... the 21-year-old was booked for DUI early Saturday morning. No word on whether he's still in custody at this point, but Caleb posed for this mug shot on his way in ... there's no question it's Ree's flesh and blood.

The exact circumstances of his arrest haven't been released, but there are other charges he got rung up on ... including transporting an open container (beer) and carrying firearms while under the influence.

Caleb's arrest comes a little more than a month after he and his uncle -- Ree's husband, Ladd -- collided head-first in two different fire trucks they were both operating, respectively. The family was battling a raging fire on their Oklahoma ranch when the two rigs crashed.

We were told at the time Caleb wasn't wearing a seatbelt ... and he was flung from the vehicle, about 70 feet or so. He and his uncle were both hospitalized, but were eventually released and seem to have been on the mend.

Ree herself gave an encouraging update on March 15, saying that they were indeed injured, but "fixable" in an update post on her famous blog. She also posted photos of the actual fire rigs in question -- which are way older than modern-day trucks, BTW -- and it loos like the impact was immense.