Cody said that despite their big age gap, Paul was "a huge influence" in his life, especially during his junior high and high school years.
"[Caleb] was the baby for eleven years until I came along, and we're closest in age. We've got two half sisters older than all of us, but [through] the same parents, Paul was the oldest," Cody explained. "When he wasn't filming, he had a lot of free time. He would come [visit] and steal me -- he'd snatch me up and he'd take me to Santa Barbara or Huntington, wherever he was living. We'd go surfing, we'd go on all these epic trips."
Caleb, 38, chimed in, explaining that Paul was "like an uncle -- like the cool uncle, you know?"
"We had a lot of fun growing up," he added. "Paul was four years older than me, so he was the big brother, the cool big brother everyone knew. I just wanted to be like him."
Paul, who passed away in a tragic car crash in 2013, was best known for his role as Brian O'Conner in The Fast and the Furious films. His real passion, however, was the ocean. Cody and Caleb tell ET that they "absolutely" feel Paul's presence, especially when engaging in nautical activities.
"We like to fish and we like to go spear fishing and surfing," Cody shared. "I feel like since it was such a big part of Paul's life, when I'm spear fishing or I'm in the water, I feel like nothing [like a shark] can touch me. Like he's totally here right now."
"I feel the same way," Caleb added. "Whenever I go surfing, whenever I go fishing, whenever I go spear fishing, I think of him one hundred percent."
"That was a big part of his life," he continued. "He wanted to be a marine biologist. That was his dream."
Cody and Caleb joked that Paul was actually going to school at a community college for marine biology, when "the acting thing" suddenly "got in the way."
"Paul is synonymous with the ocean," Cody dished. "He's known for the car thing from the Furious [franchise], and he loved cars, but the ocean is where he was at any spare moment he had."
Aside from sharing Paul's passion for the ocean, Cody and Caleb paid tribute to their late brother by filling in for him in Furious 7. Filming began shortly after Paul's tragic death in order to finish his character's storyline – and it wasn't an easy feat.
"Right before Paul passed away, he was filming that movie and he got real big," Caleb explained. "We both put on about 12 pounds."
"That first day, they were like, 'OK, now we gotta put the tattoo on,' and we're sitting there looking at each other," he continued, referencing the permanent artwork Paul had on his right wrist – "Meadow," the name of his now 17-year-old daughter, over a hibiscus flower.
"I'm getting emotional thinking about it, but he loved that tattoo," Caleb added. "It was really weird having to rock that thing for three months [on set.]"
Even though it was extremely difficult at the time, the two couldn't be more proud of how the film turned out.
"We didn't know the magnitude of how powerful it would be until we saw it at the premiere," Caleb reflected. "We both sat there and cried for about five minutes before we got up out of our seats. They did it that well."
"People loved him so much because he was so down to earth and such a normal guy," Cody added. "He was friends with everybody. He ate lunch with everybody -- they just loved him. He was just one of us, man. He was just in front of the camera."
"We love him to death," Cody concluded. "He was as real as it could be."