Wow, it's like the saying:"Living see ghost" hehe
I guess is it possible to extract the DNA from a Shizuru's egg, and inject it into a Natsuki's egg, and vice versa in the future. Or they can just clone Shizuru and Natsuki. Although if they cannot solve the problem of the shortening telomeres on their chromasomes or any other genetic degradation from age their kids will be genetically 20 years old when they are borned, assuming that Natsuki and Shizuru decide to have kids at about 20 ish.
I wonder who will carry the babies to term. I guess the fair way to do it is to have Shizuru and Natsuki carry one each. Although from the picture it seems taht Natsuki is the butch so Shizuru maybe the who carried both babies. On the other hand, if you watch the show then Natsuki is really the one who is "on the receive" to borrow a phrase from the vernacular. So she could be the one.
(Dude! are you nuts? its only a funny fan picture, stop analyzing it like a case study you mofo....OTZ)