There is also the theory that Henry had the rare Kell antigene [1], which can cause autoimmune disease and would case complications on second born babies (simil

There is also the theory that Henry had the rare Kell antigene [1], which can cause autoimmune disease and would case complications on second born babies (similar to antibody reactions with non-matching blood types between mothers and infants). It's mentioned in footnote 9. [1] https://en.wikipedia.org/wiki/Kell_antigen_system https://en.wikipedia.org/wiki/Kell_antigen_system