Baby guilt

So my older sister had 3 miscarriages. She didn't tell anyone in our family though. I ended up pregnant by accident and I was 18 weeks along when I told her. I didn't know what she had been through. She was so supportive and caring and encouraged me to tell the rest of our family. She's been the best sister I could ask for. I know it hurts her that I was able to have a baby. I've been sort of distant from her since he was born. She's such a great auntie but I saw her looking at me and my son and she looked so sad. I wish she could have all the babies she wanted. I don't want to make her sad though by bringing around the baby. She's the best sister and I feel so bad that I got pregnant and carried to term and she couldn't. She would make such an amazing mom.