For a female, this would seem to make sense–a girl receives one x chromosome from each parent, so both would factor not only into determining her sex, but her physical characteristics as well, since the contribution from each parent is equal.
For a male, this seems not as simple. A boy gets his X from his mother, and the Y from his father, so his sex is determined solely by his father. (I’m ignoring XXY and other oddities.) But are the physical characteristics of the penis, scrotum, etc. also determined by the genetic information from both parents?
My initial guess would be yes, since the proto-genitals for both sexes appear similar initially, then differentiate at some point in embryonic development. Those proto-genitals would seem to be determined by both parents.
This all came about because I realized that, if a male’s genital characteristics were inherited from both parents, I could make the extremely off-color joke that my son “has his mother’s penis.” Yes, beware of me at social functions.