To my point earlier about Gore's mom singing "Look for the Union Label": Gore used that fabrication to indicate that he was raised in a fervently pro-union house. His fib about the song wouldn't be a big deal if it weren't for the fact that his father was avidly anti-union during his stint in the Senate. Gore Sr voted for union-busting measures time after time. So the suggestion that Gore was raised to love unions is a crock.
Rubio, on the other hand, is the child of Cuban immigrants. Whether they came before or after Castro took over matters, certainly. But it does not ultimately change his backstory the way a lie like Gore's did.
Same goes for Obama's lie about his folks marching in Selma. If Obama's parents had truly been involved in the civil rights movement, then it wouldn't be a big deal that they weren't at that particular march. But the truth is that they weren't, so Obama's lie is creating an entire history that never happened.