Can Cavalier siblings with heart problems live to different ages?

My Cavalier has a grade 4 heart murmur. I recently discovered that one of her siblings had to be put to sleep a few months ago due to their heart. I'm not sure about the others although my uncle occasionally speaks to someone who has another two so I can find out when he sees her if they are still alive or not. I know that Cavaliers from the same parents with heart murmurs can have roughly the same degree of problem, but does this mean that they have roughly the same life expectancy, or can some outlive their siblings by years? I was just wondering (hoping). I know I can't expect her to live for too long because she is 9 1/2 and her heart is getting worse, but I would like to know that there is still hope for her. Please be truthful in your answers because I am prepared for the worst. Thanks xx