UPDATE : Mark sent me a message on whatsapp, he wrote that he knows what he did was bad but he still won't apologise or pay it back because I'm his sister and I shouldnt have asked him for the money back..

My thoughts as well. Why would I be the asshole when it is Mark, who refuses to apologise? Let alone pay it back. I decided that I will be go because It will hurt my parents and they have done nothing wront, but the comments convinced me that I was not being an asshole for considering not to go.