A Kamen Rider Having a Biological Child
 

What do you think they would be like? All these evil organizations poking around and altering their bodies and strange, mystical objects from long lost civilizations would probably have an effect on the child right?

Does Otaya Kurenai count?

I don't know how it would turn out. The only Riders who's descendants we've seen have been normal humans that put on magic and/or high tech belts. I'm not even sure that the classic cyborg Riders even have the ability to reproduce anymore.

The only one I can say with any certainty is that Shouichi's kid would totally be another Agito (but not Another Agito). That transformation was well established enough in the show.

Well, the cyborgs don't really matter. Those are physical augmentations on their bodies, so I doubt any children they have would be born strange.

There are characters who may have some strange children. The Arcle might have some kind of affect on Godai's children. Kouta would have some strange kids, but I'm sure he's transcended or something like that. Eiji maybe, since he did carry medals in his body, but that one is a really hard maybe...
Most everyone else, especially the modern ones, just slap on a belt or have a special power that probably wouldn't be passed on (Wizard needs a Phantom, but that's on an individual basis, anyone can become an Oni with enough training, while being a singularity point doesn't really change much unless an Imagin bothers you)

This happened in the 90's...

http://vignette4.wikia.nocookie.net/...20141115202349

...but we don't talk about that.

Oh man, I completely forgot about that. :lol

Oh, Kamen Rider Baby Shin...

I can't even imagine a rider having a kid:
"Sorry Me Jr., I can't be there for your birthday I have to be in one of those Kamen Rider x Super Sentai movies."

(Also I guess Skull had a kid but that was before he became a rider so I dunno)

And Takumi likely can't even reproduce for obvious reasons...

Shin had a kid, didn't-
That is creeepier than I remember...

But so did Wataru, come to think of it. As did Ryoutarou. So those two are good.
Takumi and Kouta may be having a bit more trouble though, both being non-human . As would Eternal, being dead. Along with a load of other riders.

Jeez, I completely forgot Ryoutaro had a grandson.

I think sometimes Ryoutaro forgets he has a grandson :p

I love how everyone forgets that one of our most recent riders has a child... Eiji Tomari, anyone?

Really, I generally think that most of our riders can still be biological fathers, as long as they're not completely cyborg or some kind of monsters (that can't reproduce).
As far as I know from the Shin Kamen Rider Spirits manga, Super-1, for example, has almost a full robot body, so he will most likely not be able to reproduce. However, as for most of the others, such as the original Kamen Riders or Amazon, I don't see why they couldn't. Shocker probably didn't have a need to take care of that and I don't think Ichigou and Nigou are complete robots inside, so yeah... should work.

As for the Heisei Riders (might not be completely spoiler-free), Kuuga is kinda out in the open, that really depends on how much the Arcle influences his body, but I do think it might be possible.
Faiz riders can't reproduce for obvious reasons.
In Blade, Mutsuki and Tachibana are fine, Kenzaki and Hajime... massive show spoilers.
Not quite sure about Kabuto because it's been so long. But I do think worms could also reproduce?
With Eiji, it's the same as with Godai, but I do believe the medals' effect wouldn't be as extreme as the Arcle, so I think he should be fine too.
As for Wizard, both Haruto and Nitoh (as well as the Mages, with one of them already having a biological child), are still humans, so no problem.
Gaim... I would say no problem there. Going from mythology, most gods could and would reproduce. A lot.
In Drive, the only exception is of course Chase.
And Ghost... well as Aran does have a father, I assume Ganma can actually reproduce? We still don't know enough about the Ganma.
As for Makoto and Takeru... they still have their physical human bodies so that should work.

Well, to be balanced, that one Mage's child was born before he harbored the Phantom (Though I don't think that would affect one's ability to have a child in the first place, anyway).

For me, the ones that leave me the most iffy are Kuuga and OOO, since their powers altered their bodies entirely (Well, Eiji's not as much, but still...).
Kouta too, but he's basically a Metron or something now.

Yeah, sure. I just wanted to name him for the sake of completeness.