Never breed any animal with an illness or defect, no matter how beautiful they are otherwise. If you want to breed, wait until you are ready, and then find healthy parents. Keep him as your pet that you love, and baby his health because he may need it.
The defect could be an illness, which then passes to the mate, fry, or both, or it could be a deformity, which then passes to the fry, or it could be an injury, which weakens him. Either way, it would be directly harmful to breed...breeding isn't just fun, or work, it is also taking on a serious responsibility to the parents and fry. You want them to be healthy and pain free, and have the best chances to survive and be sold or adopted.