Bob Saget wouldn't be the first one in his immediate family to die from a heart attack ... it's what killed 3 of his uncles.
In Bob's book, "Dirty Daddy: The Chronicles of a Family Man Turned Filthy Comedian," he references that 3 of his uncles died from a heart attack between the ages of 37 and 41.
When Bob was 8, his Uncle Ozzie died at 40 from a heart attack while chasing some kids down the block after they stole a tire.
Tragedy struck again the following year ... Bob lost his Uncle Manny to a double heart attack.
Then, when Bob was 15, he says his Uncle Sammy died at 37 of a heart attack suffered while playing tennis.
Bob also notes his own dad suffered a massive heart attack when he was a kid ... then had another heart attack just 6 months later.
Bob's family history of heart attacks may be significant ... TMZ broke the story, the operating theory is that Bob died in his Orlando hotel room of either a heart attack or a stroke, although the official cause of death won't be determined for weeks.