Jimmy Carter’s Son Jeff Shares Surprise Health Update

Just days after Jimmy Carter turned 100—becoming the oldest president in United States history—it was revealed that his youngest son Jeff, 72, has been living with Parkinson's disease.

Jeff's son Josh told PEOPLE that his father received the diagnosis some time ago, but hasn't publicly spoken about his condition.

"We know that [Parkinson's] is a one-way street," Josh said. "My dad is currently living by himself, he's able to take care of himself, he's independent, but he built his house knowing that one day he's going to need more help."

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"We're going into this with eyes wide open knowing that we're going to have more and more responsibilities going on, and it's just got to be a part of life," he added.

Josh spoke about his father's health during a panel discussion at the United Nations' International Day of Older Persons celebration, sharing more details in an interview with PEOPLE following the event.

Related: Jimmy Carter, 99, Issues a Bold Statement About the Upcoming Presidential Election

"He's not very open about it because he doesn't want to be the face of anything," Josh said. "It's just, Parkinson's sucks. It's a hard disease. It's a hard diagnosis."

According to Josh, technology has been a helpful tool for his father.

"He can literally control his brain with his iPhone, which is wild," he explained. "Without his therapy, he's basically not able to do anything. And then when he turns his therapy back on with his phone, then he can stand up, he can walk around, he can hold a drink without spilling it, he can eat, he can communicate. It's a night and day shift."

"He's able to play with my kids, he's able to play with his other grandkids," Josh said. "So, it's really fortunate to be in this wave of technology."

Jeff shared three sons with his late wife, Annette Davis Carter: Josh, Jeremy and James. Jeremy passed away suddenly in 2015 at the age of 28.

Next: Jimmy Carter, 99, Attends Wife Rosalynn's Memorial in Rare Public Appearance