Theists and atheists, how can you believe free will exists?

I don't believe in free will. It is an illusion. We may have a couple choices but those in themselves are limited. If we are born a male can we give birth and be a mother to a child? No. If we are born in a 3rd world country and have parents with AIDs, will we be able to go to Harvard? Doubtful. We are limited in our choices, free will is just an illusion.