I have produced two sets of twins. Both from the same hypo female 2 years in a row. Could still be a fluke at this point, but if she produces twins again this season I would have to assume their is something gentic about it. She is an 07 and those are her only two clutches so far. I has worked out pretty sweet though. I hit 2 pastel hypos in 09 and two double het for caramel glow females in 2010.