The former president’s grandson revealed the family secret during a panel discussion at the United Nations’ International Day of Older Persons celebration on Monday, October 7.

He explained that his own father, while supportive of Jimmy, had been unable to visit his father in hospice as much as he would like due to his own diagnosis.

“We know that [Parkinson’s] is a one-way street. 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,” Josh told People.

The Carter family acknowledges that one day soon Jeff will need a caregiver, something that comes second nature to the family.

When Jeff’s mother-in-law suffered severe memory loss after a stroke, the entire family stepped in to help. As an infant, Josh’s youngest son, Jonathan, was diagnosed with a rare and chronic intestinal disorder, and once again the Carter family was there to assist.

And when Jimmy and Rosalynn entered hospice, Jeff and his siblings agreed that their parents would never be left alone.

“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,” Josh said.

For now, Jeff is able to manage his symptoms using deep brain stimulation therapy.

“He can literally control his brain with his iPhone, which is wild,” Josh 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.”