The 37-year-old Backstreet Boys star and 29-year-old singer shared their heartbreak on social media after their father died suddenly Tuesday night.
"I am heartbroken to share the news that our father, Robert, passed away last night," Nick Carter tweeted Wednesday.
"My heart is broken, we are so hurt we lost you poppa way too soon. You were never human to me, you were always my real-life super hero #BobCarter #RIP #MyDaddy," Aaron Carter added on Instagram.
Sources told TMZ Bob Carter died of an apparent heart attack. He reportedly complained of chest pains and twitching in his arm before going to sleep Tuesday evening at his home in Florida.
"While we learn more about the cause of death, and begin the grieving process, we ask that our privacy be respected at this difficult time," Nick Carter wrote.
Bob Carter, who split from his sons' mother, Jane Carter, in 2004, appeared on the family's short-lived E! series, House of Carters, which followed the performers and their siblings Angel, Bobbie Jean and Leslie. Leslie died at age 25 in 2012.