As to the idea of each successive child in a family getting a more severe case this is a new idea to me. I would think expose to the point of becoming infected is all that matters and exposure past that doesnt matter. Ill check with some peds ID folks.
As to the strep, breastfed or not this is what docs worry about.
Chicken pox does cause about 50 peds deaths and 900 peds hospitalizations a year in the US. Thats why we see the need for Varivax. And breastfeeding.
Probably time to take this to private Email before Kathy A or Kathy B cracks the whip.
Just kidding.  About the whip not the private Email.
see next post for more BF relate topic.
-Rob