I don't think anyone knows how genetics factors into developing schizophrenia. People's genetic makeup varies a great deal, on all kinds of levels, schizophrenia or not. Personally, I think early life experiences influence how mental illness (including schizophrenia) develops a lot more than most people claim it does. It is the interaction of genetic makeup and life experience that produces the result.

So, that does not answer your question. I don't think anyone knows the answer. The only way I can think of to lessen the chances of your children becoming schizophrenic is to try to be open in your thinking about the subject, trying to understand people (including marriage partner), trying to communicate with them about everything, not hiding things "under the rug". Will that work? I don't know.