Do both parents have to be cystic fibrosis carriers for a child to get it?

Yes. Cystic fibrosis is an autosomal recessive disease which means that a person needs to inherit 2 abnormal genes in order to have the disease. Those 2 abnormal copies come one each from the 2 parents, so both parents need to be at least carriers.
Yes. Cystic fibrosis carriers do not have any symptoms and frequently there is no known falmily history of cystic fibrosis.