Maradona was Aguero's former father-in-law following his marriage to Gianinna, his youngest daughter, and was grandfather to the Manchester City striker's 11-year-old son, Benjamin.
City host Burnley on Saturday, but Guardiola admitted his star man may not be in the frame of mind, despite making a substitute appearance in the Champions League win at Olympiacos in midweek.
Guardiola said: "It's difficult for me to talk about his feelings. The game against Olympiacos was hard.
"Especially for his son, it's tough. He knew Maradona well and his son, it's his grandfather. It's a sad situation for his family, but he's OK."
Maradona was there for the birth of his first grandson in 2009. Aguero and Giannina separated in 2012 after four years together.