Guest post by "Kamino Neko" Blond hair (to simplify the genetics greatly) is a recessive trait. You can't be sure what the parents hair colours were by the kid's and can't be sure the kid won't be blond just because their parents aren't (again, simplifying greatly). Hair colour is also a result of two chemicals, and red and blond both mostly lack one of them, differing only by how much of the other they have. So a brunette and a redhead having a blond kid is certainly not unlikely (happened with my cousin, actually...her brother is a redhead, like his mom).
Aside from hair colour, Ir* mostly resembles Brunette Mom, so I'm guessing she and Hippie Dad are the bio-parents.
