All dudes have boobs. They have nipples and breast tissue. They can lactate (small amounts) and get breast cancer.
This is because, in mammals, the default sex leans towards more female. An XY-chromosome ‘male’ foetus that doesn’t respond to androgens in the womb will not develop male external genitalia, and will probably be assumed to be female on birth.
Sex is not binary, because biology isn’t simple. Gender, which is more complex than that, is not, either.