I hope they have been. Perhaps you could talk with your brother, see if he has said anything to your parents, or to your cousin. Unfortunately the final task is up to you. You haven't said how old you are, or where you live. If your under 18 there is a gay youth group you might connect with, or if your older there are some groups of newly out people.
Support groups are important, or just the support of understanding friends.
You also haven't said what kind of relationship you currently have with your parents. If it's good , setting down with them and having an honest conversation about the person you are and how you still love them but will understand if they feel bad. How you hope they can still continue with the love they have shown you all your life. If you have a bad relationship with them, you know what kind of response you will receive and need to make arrangements with supportive friends afterwards. When we grow up we start having our own lives.