A fontfamily of twelve styles seems to work just fine in Indesign. Indesign won't let me export a pdf when the fontfamily is used, though. After a while I found the Italic style was causing the problem. Then I found out, the opentype features in the Italic style are causing the problem. So Italic without opentype feature works fine, and is exportable to pdf, but Italic with opentype feature isn't.
Thing is, the opentype features in all styles have been imported from the same .fea file (except the 'kern' feature of course). I've been trying to solve this issue for two entire days now, so all help is much appreciated! I'm kinda desperate here...