My cousin just found out that her daughter is a carrier for cystic fibrosis what does this mean?

So apparently I have a little cousin that I didn’t even know I had. I met her at our family’s thanksgiving dinner. She has cystic fibrosis. I know a fair amount about the disease already, but she was wearing one of those surgical masks. Apparently she has a weakened immune system or something. I was just wondering if it was very common to wear masks like that, cause none of the people with cystic fibrosis that I have known ever did.

my sister has cystic fibrosis and i am contemplating having children of my own. my mate recalls having a cousin with the disease. What is the risk that one or more of my children will have cystic fibrosis, or is there any way to know for certain?