Re: we weren't that close, so why am i grieving so hard?
Please don't beat yourself up with questions. The answer is simple
While you may not have been close in years and/or lifestyle, you did realize a connection with him. He was your brother. You may have been a family with two kids and now you are a family of one, etc.
You have placed high expectations on yourself feeling subconsciously that you wouldn't feel anything or shouldn't feel anything and you are taken aback by what you are feeling.
Allow yourself to grieve. You grieve for the family. You grieve that he died so young. You grieve for your parents, for his friends, and yourself.
So allow yourself to grieve, talk about him, recognize him as your brother.
You may also be grieving for the fact that you lost any opportunity to have a different relationship with him. Maybe subconsciously you may have felt that you had time to change the existing relationship with him for one you wanted to have.
Allow yourself to grieve for you have lost something even though you may not know exactly what that is right at this moment.