This story has a point or two but why be so bitter… there are bigger issues to be annoyed about or maybe your life’s so smooth you don’t have those issues. Also [adding to my own comments a few days later] how often does this happen? Maybe once or twice in a lifetime? Say there is a period of 5 years or so when there is a risk of someone doing this terrible thing (bringing a sibling to a party). Let’s say you have two kids so the risk doubles. Twice in your life you will have to go through the unbearable akwardness of having to accommodate an uninvited kiddo. Ok, You feel how you feel — angry with the parents. Still too much anger in the grand scheme of things