okParent _       (FamInstTyCon _ fam_tc tys) = tyConArity fam_tc == length tys
okParent _       (FamInstTyCon _ fam_tc tys) = tyConArity fam_tc == length tys
okParent _       (FamInstTyCon _ fam_tc tys) = tyConArity fam_tc == length tys