It's an easy thing for me to let go. Since I could lose the only sibling I had, I don't think I have the power or influence to make anyone stay. We lose people voluntarily and involuntarily and at this point, it's what it is, and one has to accept it. 
Everyone has a path, and sometimes as we change, it might not colide with the path of others. I wholly accept this. Thanks for for the kind words.