(CNN) To lose a brother or sister while growing up is painful enough. When it's the result of gun violence, the weight can seem insurmountable.

It's a burden often overlooked with every new headline about bullets killing children.

Kathryn "KC" Conway knows the pain these surviving siblings carry. For two decades, she's worked with the Center for Grief Recovery, a Chicago-based nonprofit that began by focusing on sibling loss.

The forgotten victims of gun violence When children are killed by bullets, grieving parents are often the focus. Yet there are other vulnerable survivors whose voices are rarely heard: the young brothers and sisters left behind. Theirs is the untold story of this American tragedy.

When a child loses a sibling in an instant, Conway says, the trauma can arrest development, emotionally or physically. It can also complicate or delay grief.

The experience is different than losing a sibling to terminal illness.

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