Trying to conceive. i have a bro w/ severe autism and a nephew w/ mild autism. would my baby be more at risk?

Impossible to know: Unfortunately we don't know what the cause of autism is so your question can not be answered fully. There is no test for autism that can be done during pregnancy or before at this time either. I'd focus on what you can control such as: trying not to worry, eat a well balanced diet, avoid alcohol, tobacco, and other known substances that can injure a baby, and do not travel to Zika infected areas