18 and Pregnant

Cl
I'm 18. My brother got married about 2 years ago and joined the marine corps and had a son this past April. His wife and him are separating. She had their baby last so she has custody now and won't allow my family to see the baby. I found out 3 days ago that I am pregnant. I have to tell my parents that I am pregnant. But I don't know how to do so because I'm worried they will think poorly of me because of the situation with my brother or that they won't be happy or approve. I don't know how to tell my parents. How should I go about it? Write a letter? Send them a text? Just tell them? Make it a surprise?