I have two male characters, A and B, who are discovered to be half-brothers (they share the same father) after a family medical crisis that takes place when both are in their 20's. However, their mothers are also half-sisters. (The boys each have one older sister, but the girls have different fathers than the boys.) But how exactly are they described in regard to the genetic aspect of their family relationship? half-brothers *and* first cousins? Or something else entirely? And just how close is their genetic code related to each other? 75% or higher?
I hope this hasn't been too confusing. Thanks in advance.