A good friend of mine told me a couple of weeks ago that she's pregnant. I was so happy for her I almost cried- also because this is the first time someone I'm quite close to is having a baby.
A few days ago she had her first midwife appointment, and texted me right after to tell me incredible news- it's twins! I was shocked and amazed and incredibly excited for her.
This evening she just shared the news on a group chat we have with mutual friends, and it suddenly just hit me and I started crying. The thing is, since I was a kid, for some reason I've always loved the idea of twins, and as my mother lost twins, I know there's that slightly higher chance... Whether reasonable or not some part of me always felt twins were part of my destiny. I know how silly that sounds. I've had 4 beautiful babies and I am utterly grateful for them, yet each pregnancy I wondered if it could be twins, and each time when I found out it wasn't, a part of me couldn't help feeling sad 
Now I'm going to watch my friend live this experience that I've always wanted, and I know I won't have, now (my health won't allow for another pregnancy). I'm so happy for her, but I feel like I'm now grieving what I'll never have. And of course I know it's unreasonable for me to be sad about this when there are people (like someone very close to me who I love dearly) who can't have children at all, and here I am with my big family.
Has anyone else been in this situation? How do I deal with this sadness?
I have no intention of ever telling my friend how I feel, I just want to be supportive and kind to her because she's amazing and I know it'll be hard work and not easy for her.