Sadly enough, the only Ranma/LinLin&RanRan story I could find was "Psionic Ranma" at
Http://stfan.free.fr/[/URL]. This is a hentai story gallery that hasn't been updated since 2004.
I don't really recomend this piece because even though it has that pairing, the plot is basically MIA. It is a harem fic that features BDSM and humiliation aspects to it's sub-par plot.
I know it may not be what you want, but at least there is at least one out there. Even if it is a, in my opinion, POS.
If you want to see it, drop the first http.