Oh lionmummy, YASNBU. I am so, so sorry for your loss.
It's horrible. I had my last MC in Jan 2010. DP's brother announced his partner's PG exactly 2 weeks later.
When they had their baby, all I could think was 'I should have a baby now too'. Selfish, I know, but I couldn't help it. The morning their baby was born, DP and I were helping his folks collect some furniture. By the time we met them at 10am, they had been to the hospital, and taken so many photos of the new arrival. Which DP's Mum showed me, in the middle of a furniture store. I had to feign a nosebleed and run to the car for a great big cry.
Then, it was demanded that we go to visit at the hospital (by DP's brother). Having this beautiful, 10 hour old little one thrust into my arms almost ended me.
How to deal with it? I really don't know, tbh. I kept my distance for the first few months (which led to accusations of me being a horrible, cold, uncaring bitch by DP's brother). I just couldn't hold their daughter.
Now, many months later, I can handle being around them, though I still cannot hold their daughter.. It still hurts - I reckon it always will, but I can at least be around them, without wanting to cry, or yell, or throw things.
So sorry for hijacking your thread, OP.I just hope that sharing my experiences will help you.
It will be difficult. Try to be strong, and enjoy the new addition to the family. PM me if you want to talk about this further.