I'm sorry that your family has another member dealing with a Head and Neck cancer. There are many here who have Stage 4a. Due to the insidious nature of this disease, many diagnosed with Oropharyngeal - throat cancer - are Stage 4 already when diagnosed.
My husband was stage 4a. His tumour was huge already. He was only diagnosed when he started to slur his speech as a lymph node pressed on the Hypoglossal nerve. That was 4 years ago this month. Kris is alive and well as are very many others here who were also Stage 4.
So, have hope. Surprisingly, many who are only stage 1 at diagnosis don't make it. You really can't tell. I too thought Stage 4 was a death sentence . It is not. There are many factors that come in to play. So, be hopeful.
Keep coming here, we will all help as much as we can. Also encourage your cousin or her son and his family to join. I did not find this forum until we were just finishing radiation/chemo. So wish I had found the boards from the beginning.
Thinking of you,
Tammy