I had a son 38 years ago who only lived for 15 minutes. It was very hard for me to grieve because after the initial death no one I knew acknowledged that he had ever been.
My daughter lost a son to Twin to Twin Transfusion Syndrome (TTTS). It is a condition that happens only to identical twins.
She became involved with the Fetal Hope Foundation.
http://www.fetalhope.org
There is a section for stories of survivors. Hers is under the title of Zachary and Nicholas.
They do have a blog to help with bereavement. A place where people can talk of their loss. If the babies were identical twins this would be a great place for the family to go.
My grandson is now 6. We do talk about his brother.