Unsure what to do

My ex is getting married next week and he wants to see me. I asked him why and he said he just wants to talk to me. He said he just wants to apologize for how things ended between us and how he realized you don’t know what you have until it’s gone. He said he loves his fiancée but I will always hold a special place in his heart. I told him I don’t feel comfortable seeing him

since he is about to be married. Should I his fiancée? I feel I would want to know in her situation but I really don’t know what I should do. Why is he doing this?