Half-orc brother and half-elf sister?

[domino]

Two half elf siblings. One died, reincarnated as a half orc.

Or vice versa.

 

[RandomPrecision]

Yes, what is your point? Half-Elves are NOT a species, they are a Hybrid of 2 species. Species breed true. Hyrbrids don't. You'd expect to see 25% Humans, 25% Elves, 50% Half-Elves.

Sure, if there's one gene for "species". I don't agree. Half-elves have societies. Half-elves have half-elven children. I don't think we should use sophistry and science to remove half-elves as a race, despite how I don't really prefer them over any other race in D&D.

Though we speak like that occasionally, nationality isn't determined by genetics.

Then substitue racial groups as you see fit.

Perhaps the best illustration of something like this is a genetic disease like Tay-Sachs or Sickle Cell anemia.

Exactly. Those are located on one gene. I'd assume that humans, elves, and orcs all have more than one gene that determines their physical makeup, although I don't think genetics should be a strong emphasis of D&D. That's one reason why I don't think Punnett Squares should be used, the other being that if we allow any scientific thought into the matter, it's obvious that this isn't what happens.

And so on, the other quotations are exactly what I was saying. Punnett Squares work fine on simple genetic situations, like Tay-Sachs and Sickle-Cell Anemia. For the entire half-elven and half-orcish genomes however, this does not work.

 

[Dannyalcatraz]

Then substitue racial groups as you see fit.

In humanity, Race ≠ Species. Race is, essentially, subspeciation. The difference between a black human and a white human is basically the same as between 2 breeds (subspecies) of dog. There is simply no RW analogy for modern humans crossbreeding with other species of primates. Though some scientists have proposed that Homo Sapiens Sapiens were capable of crossbreeding with Homo Sapiens Neanderthals, there have been problems with the non-Mitochondrial DNA samples that have been recovered and attributed to Homo Sapiens Neanderthal.

Once again, I can only return to things like my Swords and Platys, or whales and dolphins, or or crossbred Tigers & Lions, or even the various equine crossbreeds. Note that the hybrid equines exist between species that don't even have the name number of chromosomes (see my previous link).

When the hybrids are not sterile, their offspring tend towards the 25/25/50 split...in conception. Whether the offspring are even viable is a different issue.

Half-elves have half-elven children.

I don't know where you get that from. Not that its wrong- the square predicts 50% Half-Elves from a pair of Half-Elf parents. However, the only thing I could find in the Core books on Human/Elf/Half-Elf genetics is:

Most half-elves are the children of human-elf pairings. Some, however, are the children of parents who themselves are partly human and partly elf. PHB p18

 

[Three_Haligonians]

Wait a minute, why can't it be that Dad was is a charming lich and it willing to anything with the appropriate gender, using polymorph to get the job done?

The lich lech!

Don't mean to get too graphic here, but . . .

Any part of the body or piece of equipment that is separated from the whole reverts to its true form.

R from Three Haligonians