Most likely, when I was pregnant with Sydney some of her blood made its way into my blood and my body thought it was something it needed to create antibodies to destroy. She may have had this same thing the boys have, but she didn't show any clinical signs of it because the antibodies my body created weren't strong enough to harm her. But when the boys were placed in my womb, my body responded quickly and started producing the antibodies it thought it needed to destroy the "virus." These antibodies then got into Brock and Braden's blood and started attacking to protect me from them. Since they were introduced earlier in the boys' bodies, they had a much stronger effect on them than they did Sydney which is why we are having the hemolytic anemia.
What all this means is if we ever got pregnant again and the baby (or babies) had the same blood type as Brock and Braden, the antibodies would start attacking even quicker and the baby could possibly die. This also means that the jury is still out on fraternal or identical twins. Sorry, Sandy.
And I had the chicken pox. Twice.