"A brave man´s blood is the best thing on this earth when a woman is in trouble."
No, that´s not how blood transfusions work:
Either the woman is AB negative and a universal blood recipient (which is highly unlikely, because only approximately 4% of earths population have this bloodgroup) or the four men all have the same bloodgroup of 0 negative and thus being universal blood donors. And this is even more unlikely.
I guess I have to accept that Luca Westenra is so special that her bloodgroup actually is AB negative.