Why do i feel like its my fault that my mum and dad and sister died in a car wreck?

My lil sister just got her licence sje wasn't the best driver and she was gonni take me and my mum and dad out and my mum sed I could drive them there and my sis could drive us back and I sed I can't come I have to go out with my friends and they went and idk what exactly happened I'm sooo ***** sad I know its my fault iv had my licence for 4 years and I am a good driver I'm carefull on the road and if I just went with them they could of still been here today !!!!!! Is it my fault !??!?!!