It's possible this happened then, but "chemical castration" is not anything like actual castration. His dad supposedly got him an injection to treat acne, which is an androgen-dependent condition. The drug he was supposedly given would reduce the effects of testosterone by blocking its interaction with the androgen receptor. It stops doing this when treatment is discontinued, so the effects are generally reversible. Getting some shots as a 12 year old didn't make MJ a sterile castrato, despite what Joe Rogan thinks.