My thinking on this is as follows.

It isn't that it is so important to us that our family "understand", it is important for us to see that they are trying.

My mother cared enough to try to educate herself about 'the PTSD". What it is. How it affects my life. What to expect in the way of reactions from me. Her efforts to
try to help me, if possible, meant more to me than anything she has done in a long time.

I think it is the effort put forth to understand and care that means the most to us
Knowing they CARE is the key. Feeling like they don't is what hurts us. Just MHO