[Monica]

That would make both cockatiels about 5 months old... Have they gone through their adult molt yet? If not you may not be able to truely tell until they do. Do you know the parents mutations? Or can you get a hold of the breeder to find out the parents mutations? If we know the parents mutations then we could better figure out the sex of your cockatiels, since both lutino and cinnamon tend to be sex-linked mutations.