As I've stated in other similar threads, if as implied by the existence of half-elves and half-orcs, D&D genetics roughly follows the same rules as RW genetics, you would expect an orc-elf hybrid 25% of the time if half-elves and half-orcs can interbreed with each other.
Of course, there is also RW precedent for such a cross to be sterile or even non-viable & stillborn.
As I recall, that dates back to the dawn of D&D, when almost all Orcs were evil destructive barbarians by definition, making a positive, "normal" background for a Half-Orc nearly impossible.
Civilized Orcs are relatively new to D&D.
Of course, there is also RW precedent for such a cross to be sterile or even non-viable & stillborn.
More seriously, I'm not sure why everybody assumes half-orcs are the result of rape. Orcs in Eberron are a perfect example of socially acceptable orcs.
As I recall, that dates back to the dawn of D&D, when almost all Orcs were evil destructive barbarians by definition, making a positive, "normal" background for a Half-Orc nearly impossible.
Civilized Orcs are relatively new to D&D.