According to the health survey conducted by the YTCA, dry eye (KCS) is the second most common eye problem in Yorkies.
Health Survey 2007
Genetics are very complicated and breeding is a huge responsibility. It's now very important that you find out from an ophthalmologist exactly what the puppy has. Depending on the diagnosis, his parents may have to be altered and retired from breeding. You should also contact the person who bought his brother and make them aware if this turns out to be a genetic condition. In this case, you should expect to pay for his brother's eye exam also.