Half Breeds

Try asking /d/

Without the ability to change shape (because it's a tremendous cop-out and also really dumb for dragons to do), there's obviously some size difficulties. If we assume standard one human parent situation, then young dragons before they get too big can awkwardly, but successfully mate with an average human of the appropriate gender. After a certain age, male dragons get too big, though female dragons of any size technically still can but it just gets more and more awkward and less likely to succeed.

One extra complication for when the dragon is the mother, but half-dragons infants are not able to break out of the egg on their own (at least not half-human half-dragons) and so very carefully and with timing of critical importance, the egg must be broken to retrieve the newborn. Also of course, nourishment of the infant is a concern with the mother unable to produce milk (not a mammal) and the infant itself unable to do something like chew and eat on its own as well as a full-dragon newborn would. Like, the half-dragon infant can't just be brought/dropped a dead rabbit to eat on it's own, for example whereas a normal dragon infant could.

You cream in its muffin with your bratwurst.

Some ritual is performed where the devil or demon can be summoned to the material plane with a material body, usually for the explicit purpose of breeding. A mortal lays with the devil or demon, the ritual ends and the entity returns to where it came from. A mortal mother can just carry the half breed to term, a mortal father either has to re-contact the mother with summoning when she is to birth the half-breed so can do so in the material plane, or the mother just births the half-breed in her realm and then either sends the half-breed to the material plane at some point or again via summon ritual goes to leave the child.

Yes, it stings a demon to have holy water on thier skin, now imagine how painful it would be to have a human soul gestating inside them.

They fuck?

youtube.com/watch?v=3E0ec_FwhmY

Source on that please.

Depends on edition. In 1E, 2E, 4E, and 5E, it makes a Cambion. In 3.0 and 3.5, it makes a creature of the base race with the Half-Fiend template.
Outsiders can breed with nearly anything. It makes Planetouched. But Celestials and Fiends specifically make Half-Celestials and Half-Fiends (and then their children make Planetouched of Aasimar and Tiefling varieties).
>"BUT ANOOOON, THERES NO EXAMPLES N SHIT"
What the fuck, there's examples all over.

Mostly rape from chromatic dragons, occasionally falling in love from metallic dragons. Metallic dragons shapeshift, chromatic dragons do not.

>Carefully.
Actually, they're hardly careful at all and just try again if the mortal dies. They are evil.

An Encyclopedia of Fairies, Hobgoblins, Brownies, Boogies, and Other Supernatural Creatures, by Katharine Briggs, and a compilation of arthurian stories which I read some 3 years back

Probably helps to start cultivating trust and dependency at a young age.

(You)
>>"BUT ANOOOON, THERES NO EXAMPLES N SHIT"
>What the fuck, there's examples all over.
Just acting on the hypothesis that OP would say that

Depends on the setting

>Due to the lifespan differences between a fiend and a mortal all said relationships start with grooming

Demons love souls, there's nothing to say a soul has to be naturally inimical to them, particularly if it's a tainted one via a fetus grown from their own flesh and sharing their blood.

...

Demons are literal Chaos and Evil incarnate to the point where it's an intrinsic aspect of their beings held in stasis until it snaps in on itself at point of death.

As far as I've been lead to believe there seems to be evidence to support the notion that both strains of Evil outsider literally just 'will' their genitals in/out when they want too as a part of the fluff.

Ironically, Graz'zt, Son of the Pale Night, and fucking NYRALATHOTEP is the only Demon Prince I know of with consistent gentials, literally having dedicated COCK armour when he decides he really wants to humiliate a party of angels contesting his realm in a manner that is "Literally fights like it's a DMC game" combat style, which is the only thing that can scientificaly explain how in the fuck he competes with monsters so powerful that the single fact that can drown opposition in minionspam alone is enough to worry about, next to the absurd ammount of lore generated on their powerbases that has carried over the generations, when all this guy has to his name is hatefuck wife, Evil son, and pleasured a goddess no one talks about anymore on his resume.

Half-Demon Half-Human

Evil doesn't mean careless. Given the choice between taking a few hours for some prenatal magic preparation or spending a month murderfucking women until finding a sturdy enough one any demon who really wants a kid for some reason and isn't just doing it for fun will choose the former.

Hell is big on rules and regulations and enforces consistent child-care support "for the benefit of the growth and development of the child in furthering the mission of the empire of hell." For this reason only mostly demons sire children.

Devils tend to "taint" the children of warlocks instead as a workaround.