My fear of still birth

They say still birth is so rare; but how rare is it when my sister in her 20s had three still birth after a completely healthy pregnancy at 21 years of age. How rare is it that my cousin have had 5 and she's only 28 years old. And yet again I know other young women who it has happened to. I can't sleep at night because I know too many people whose had at least one or more still birth.