I come from a huge family, with over 45 first cousins, & not one other person has ever had any type of autoimmune illness. My neuro told me that CIDP is not hereditary. If you didn’t notice much improvement from the IVIG then it is possible that you might have the progressive form of this illness. Not to scare you, but it seems that those who have the relapsing/remitting form are the people who do the best on IVIG. Not that you don’t need it, as it does tend to halt the progression of the illness.
I am sorry you have a child so young; my youngest of 3 was 21 when I came down with CIDP. I had already had the pleasure of teaching my children to ski, skate, play tennis, etc. As for the fatigue, there really isn’t much you can do about it, we all seem to have it, just get as much rest as you can. And don’t push yourself, you will only suffer more for it later.