Does Pre-Seed increase the chance of twins?

Pre-seed does not have an effect on ovulation, as such, it would be unrelated to the occurrence of twins. It does have an effect on the potency and vitality of sperm and increases the likely-hood of conception. If you are interested in having twins, Clomiphene and Gonadotropins are commonly used fertility drugs that can increase your chances.

Currently, there is no scientific evidence that Pre-seed will help you conceive twins. It can help the sperm find its way to your egg and as such increase the likelihood of pregnancy. But that is as far as Pre-seed goes, it can't aid the body in the conception process.