Well if there was no Charlemagne then that means he never had a daughter, and if there is no daughter then there is no marriage to the Norse chieftain Rollo, which means that the entire history of Normandy in France is a lie!
It also means that I shouldn't exist as I am now not descended from Charlemagne (my family tree can be traced through Robertus de Villapari vel. de Sancto Leodegario and the family story has always been that the St Leger's were descendants of the bastard son of Geoffrey of Eu, one of Richard I of Normandy's sons).
To be honest it's not that big a deal either way for me... my ancestors gambled the money away on stupid expeditions to Eldorado with Raleigh (a distant cousin), and then had too many daughters so the rest was spent marrying them off.
And before anyone asks - no I am not rich and did not go to a posh school and university. I am working class and wouldn't have it any other way