At least, player breeding is what a guy on my team likes to call it. He just likes the idea of having sex in the game, but if its going to be there, I'd like it to be more in depth than that. What about pregnancy, babies? What do you guys think is the best way to deal with this subject in a multiplayer rpg, if at all? Do you include sexual diseases? What about inter-species? What do you do with the babies, or do you just make the females sterile? If you allow the players to have kids, are the kids PC's or NPC's? Maybe both? Do the kids get any bonus's to skill from the parents? What happens when the parents die? Do the kids turn into NPC's, disappear or does the PC take control? What are you guy's thoughts on this topic?

Fable 2.

If it wasn't the least subtle (and least effective) attempt at controversy, then it was probably the most boring and least rewarding of the features present within the game.

Skip it, do something good with your time.
Only make sex an integral part of the storyline and leave the porn up to rule 34.
It worked for Mass Effect. In a way.

You could make childhood an integral part of the game, and require players to have babies if they want any more than X (2 or 3?) initial characters. This would enhance the importance of each character because of the time and effort players have put in to raising them.

Do you include sexual diseases? Yes!

What about inter-species? Depending on the # of species, yes! With too many, programming in all the small genetic differences would be hard or near impossible. This could be fixed by setting a lower limit on how much of a character's genetic makeup can be from one species (any less than 1/4 and it does a coinflip, for example). What does a 5/32 wookie, 13/32 human, 14/32 orc look like?)

If you allow the players to have kids, are the kids PC's or NPC's? Maybe both? Both. Non-aging Tamagotchi NPCs until you decide to take control of them, and then PCs.

Do the kids get any bonus's to skill from the parents? Yes!

What happens when the parents die? Do the kids turn into NPC's, disappear or does the PC take control? If the parents die while the children are NPCs, they could just disappear, or be put up for adoption? If the parents die while the children are PCs, they should gain a new descriptor (orphan?), and continue playing.

Hopefully this gives you some ideas. Keep us updated, this sounds like a cool project.

In the lore in quite a few things humans seem to have the advantage of being able to pair themselves with just about any sentient race(even man eaters like demons), while other races almost only pair with themselves.

If I were to make an RPG I'd probably take something like each character only having so long to affect the world, then if you did manage to have children(anything from a serious relationship to some whore's child) you'd get to choose one of them to play as. Of course this leaves the problem of how to manage dynamic story lining based on such.

I certainly wouldn't include incurable diseases. Curable ones I guess you could play for comedy, comparable to the appearance of cockroaches in the sims. But I can't imagine how a serious treatment of stds would contribute to a game being fun.

Interspecies I would certainly include, since I think a lot of players would consider that fun.

I'm not sure it would really be an RPG to make children playable - I'd design them to be more like a collection of vanity pets, something to make a player's house seem more alive and homey, and in a humorous way they're like trophies.

Breeding lends itself perfectly to moving from human(oid) roleplaying to a more animalistic form. Imagine players are wolves. What kind of gameplay could the feature "breeding" provide? Mating rituals, that, if followed properly, provided bonuses to the starting stats of the pup; DNA strings that feature somewhat like savegames, in that your main character may die, but they live on in their offspring's DNA (which further affects a pup's starting stats).

First, start by better defining your audience! If you are talking about a younger audience then be very, veeeeeery careful, but if you are targeting a mature audience (specifically, mature GUYS) then I say go for broke or use the overall theme for your game to come up with proper creative constraints. The one thing I would avoid, unless you are going for a REALLY adult game is player avatars having virtual sex with other player avatars. That opens up a realm of nightmares on the public relations side.

Sexual diseases? Sure, why not (but make them curable).

Inter-species? Of course. Make it into a chemistry experiment. Heck, if the child isn't going to eventually become a new player avatar then have some good combinations, and some really bad ones, or even silly ones. I mean, if a human avatar mated with an ent NPC, then maybe our offspring is something akin to Pinocchio. Seducing an Ent could certainly be an interesting encounter! What do tree people find sexually attractive?

PCs or NPCs? That depends on the story as well as the system. Be prepared to weave the kids into the plot somehow if they are to become player avatars, that is if the parents are getting such treatment in the story.

Inherited traits? Sure, if they are to become player avatars or can contribute to battles as henchmen or minions. Otherwise it might be a waste of time.

What happens when the parents die? Hard to say without answering a lot more questions about your game, but I'd avoid forcing the player to assume a new avatar unless you really have thought through the ramifications. I think most players will enjoy being able to control different avatars, but losing an avatar that they like, even if it means they get a new and better one, is a hard pill for them to swallow. People get attached to their avatars.